Another DK option I forgot to mention is Bair, land behind UpB. Ungrabbable, unshieldable (at least fully), undodgeable, and it kills all pikmin. At low % it easily racks 15-20% on Oli.
With DK, he has enough options out of SH Bair to keep Oli guessing between shielding, grabbing, and spot dodging. If Oli guesses right, he can land DK with 20-40% correct? If DK guesses right, he can do anywhere from 15-30%, and puts Oli in the air where he can take advantage. All DK needs is to rack up 70% or so to kill. Olimar needs to rack up at least 100%, if not more to effectively kill DK. (What are Oli's kill %'s on Upsmash/Fsmash/ Bthrow btw? I can't keep track of the different stats for each color pikmin). As such, on average these exchanges start working slightly DK's favor, as he needs to rack less damage to KO.
Also, keep in mind SH Bair isn't his only approach for Olimar, but I do believe it to be his best. DK can always empty SH, or Bair then land, and roll behind Oli and punish a shield grab/fsmash, or Bair, airdodge. In the event that DK gets hit with a pikmin after the initial Bair, he can simply DJ away and Bair to clear the pikmin. It doesn't do much to press his offense, but it lets him escape with only a few % damage and resets the stage.
In my mind, I see any moves not directed at olimar as advantageous for him. The slightest lag on his opponent's moves set them up for combos, and KO's. This is a very important aspect to Olimar's play-capitalizing on moves not directed at olimar. The range on his projectile, and his grab allows him to punish correctly.
This is true. The usage of SH Bair is only for spacing purposes. In the unlikely event of Oli jumping and trying Fair, he gets outranged by Bair. It also serves as a sort of "timer" for me, so I can judge my spacing and distance on a followup hit. There isn't much Oli can do against a SHBair other than toss a pikmin onto DK. Anything more than one pikmin and Oli eats another Bair in the face. One pikmin will only rack up maybe 5-10% before DK is able to remove them. Also after the initial Bair, DK can always airdodge, land and roll/shield as well to avoid attacks.
This is all assuming olimar doesn't keep his spacing properly and DK closes in properly? If so, then yes, DK should be able to kill olimar decently. If not, Olimar is quicker and can maneuver around the bigger characters in brawl easily and continue to throw pikmen to setup for even more damage if killed while not attacking olimar. This is, if olimar can space properly though. I don't see DK as being able to close in on characters that partly rely on their range game to beat bigger characters. He can force the issue on some select characters without a great range game like olimar has, but overall(imo) I don't think DK can take it. He has his approaches and all, but many of them are avoidable by simple dodges and roll dodges.(ex. being bair, sideb-can be avoided by shield, spotdodge; bair, jab-avoided by rolling.)
In reality, if a grounded olimar stays grounded and doesn't move very often, the DK will most certainly win, as will most character. The combination of his pikmen throw, shield grabbing, grab range of his pikmen, range and speed on smashes, and his great aerial game, and his VERY underrated approach game(to mix it up) is enough to give olimar the advantage in this matchup, i feel.
Most olimars will stay grounded. They'll also throw pikmen and shieldgrab like you mentioned. Olimar players also SHfairs more than people realize. It has great priority and makes a GREAT approach for those times when olimar is near the edge. The general consensus around the boards is that all olimar does is camp and throw pikmen and wait for people to come get him. They attack, either successfully or get shieldgrabbed. It's very bad to assume olimar players will continue to do this. Did you know that everytime you hit the pikmen, you refresh your moves? This should be enough to get every olimar main to throw pikmen and follow up by either grabbing, fairing, throwing more pikmen, fsmash, or even tilts(occasionally if they space wrong) Not just let olimar's opponent keep trying to fend them off.(unless the pikmen can get enough damage to make it worthwhile. It forces olimar players to attack after throwing. Your job, when fighting olimar, is to somehow attack olimar as he and his pikmen attack you. This is what it all boils down to. This is just about the only variety that olimar players get: choosing how and when to either approach and evade attacks while throwing pikmen to taunt their opponent.
How exactly does Olimar run away and maintain spacing though? If you stick to ground run, DK can always just follow with Bair and keep the same approach. You have to either stop or jump to be able to pikmin toss, which is where DK Bair will catch you. You can't rely on SH Fair either because again, it is outranged by DK Bair, or can be blocked, then punished with Utilt. DK can also stay on the ground and follow behind if Oli runs as well. It gets tricky because Oli can pivot grab, but DownB outranges grab, you have to stop/jump to toss pikmin, which gives DK time to turnaround Bair, or run under him and Utilt/Dsmash. If you stop and do Dsmash/Fsmash DK can shield, jump over with Nair/SideB, or Punch superarmor through it. UpB also has invincible frames on the startup, which can eat the hit, then beat out a shield or spotdodge from Olimar.
Also, I play DK to capitalize on shielding and roll/spotdodge. DownB pressures shield and beats a spotdodge/roll. UpB will eat shield stab and lasts long enough to catch a roll/dodge.
Another thing I'd like to point out is olimar's textbook combos v large character. The most basic being the first one. These are much easier to carry out on the larger characters b/c their hitboxes are easier to hit with the following.:
dthrow, upair or fair
grab,dthrow, fair, ff,grab,dthrow,ff, hyphen smash, upair, upb(low percentage to rack damage. after the second ff, it's possible to DI out of it, but that invites another grab dthrow, fair or upair combo.
uptilt, upair, upb(this is great for juggling large characters. It's one of olimar's many moves that keep his opponent airborne.)
nair, upair or fair, upb(depending on DI)
dtilt,dtilt,upair(it's basically only at low percentages, but dtilt can always be used until about 100%? to combo into an upair.
(Could you list damage estimates on these for me?)
Oli does have good combos on DK. DK doesn't have so many combos, but he has a lot of setups and 50/50s.
Utilt at low % (0-20ish) leads to another Utilt for 15-20%. After this you have a solid mixup game. You can go for another Utilt, which can be airdodged, but if they airdodge you can slightly charge a Dsmash, set up SideB, DownB, or UpB, dealing anywhere from 10-25% damage. From 0% if you guess right here between airdodge or no airdodge, you've already got Olimar halfway to where he needs to be to KO'd.
Dthrow also has options. Dthrow then dash leaves oli with the options of: DJ, land, airdodge, attack. DK dash attack beats land and often attack. Dash in shield gives him another grab unless Oli airdodges. Up and DownB work for all options other than DJ. 7% for the throw (without grab jab) then 10-20% for the followup. Again, puts Oli at the halfway mark to be KO'd.
These are probably the most reliable setups for Olimar, due to his size, but if you land one of these setups and guess correctly twice, you have Oli at just about where he needs to be damagewise for the KO. All you need is to land one or two more hits, like a tilt, Down or UpB, or a grab, then he's ready to go. And KOing Oli isn't that difficult. Dsmash alone kills reliably around 85%, and is fairly easy to hit. It's quick, and covers DK nearly all around. You can roll through grab/smash and land it, you can catch Oli if he takes to the air.
This isn't even mentioning Olimar's terrible recovery. If you can get Olimar off early with Dthrow/Bthrow/Bair, DK can hop out, kill Oli's 2nd jump with Bair/Nair, and edgehog. Yes, you can DJ+airdodge, but DK has the aerial mobility and Bair can be fired off twice to catch Oli after he comes out of airdodge. Also, if DK gets a grab near the edge at 40% or above, he can cargo stagespike Oli on a lot of maps, then UpB to the edge, giving Oli virtually no hope of recovering. I notice in a lot of Oli matches Oli will camp towards the edge, such as under a platform in Battlefield, so this technique isn't very hard to pull of.
I still think DK holds at least a slight advantage in this matchup. No, his approach won't work on Oli 100%, but he has enough mixup to keep Oli guessing. All it takes is 3-4 wrong guesses on Oli's part and DK easily racks up the 70-80% needed to kill Oli. Dsmash alone will get the KO on Oli. He can get early gimp kills through edgeguard and cargo stage spike. Meanwhile, Oli has to camp and runaway, and has to catch DK messing up quite a few times before he can reliably get a kill. Pikmin toss is annoying, but unless you are able to get a grab(which Oli undoutedly will), the pikmin is only going to deal at the highest 10-15% or so before it gets removed. This works great for damage racking on most characters, but against DK, who is one of the heaviest in the game (THE heaviest according to M2K's weight tests), you need to rinse your damage dealers a few more times than normal before you can kill DK. If you do not kill DK, he will come back, and more than likely deal some more damage before you can send him off again.