Kasai
Smash Journeyman
ok,
1. dk is not nearly as easy to gimp as you assume, the only characters that can consistently hit him out of upb are marth, dedede, yoshi (eggs) falco (laser, not an aerial), wolf, ike, pit and olimar. the rest get out ranged and out prioritized by the upb
I'm fairly certain (not 100% because I haven't specifically tested it and don't play against DK enough to have it as common knowledge) that lucario's dair will go through DK's upB. As I have seen so far, it goes through about everything (including snake's "semi super armor" that his upB grants him. If not dair, bair would definitely do the job.
Just stating that stagespikes are common isn't relying on them.2. don't rely on a stage spike, they can come in high, they can sweetspot the ledge before you hit them, and they can tech the wall. and dk is not going to come in low enough to be stage spiked by lucarios dair
The kill at 60% is from pure gimping alone (so lucario can be at any %((The higher %, the lower he can do this at, 60% being when lucario is at 0))). Something as simple as dthrow/bthrowing off the edge followed by two or three fairs followed by a dair... Even without the dair, it could be possible that DK might not make it back due to his lack of vertical recovery.3. i guess he could kill at 60 if he was at 200+, but the likelihood of that is low, especially considering dk kills lucario at low percents, which is my main point that nobody has addressed
Edit: I'm turning on brawl right now to test rough KO %s (Without DI but just for general reference).