Doc is great in this game imo. All of his smashes are very good. Usmash is basically safe, damaging and a nice ko move around 140%. Fsmash decreases his hitbox because he lunges back, so any predictable fair /tilts/grab can be dodged into this smash. Ko's really early as well :0
Pills are a great deffensive tool and force a lot of characters to approach. Especially handy against DDD since the pills bounce and make it hard for him to throw gordos without bouncing them back.
Cape is very good,very fast startup and doesnt change his momentum. Which is nice for if you're fastfalling and miss to counter the projectile.
His tilts are good, very fast and utilt combos great.
Throws are awesome, dthrow into dair/uair is amazing. I do wish his bthrow would kill a bit earlier though
Aireals are insane. Yo I cannot stress enough how good bair is. Dair is amazing for spotdogde happy people as well.
Upb oos is amazing at high %. Down b is amazing for landing and predicting spotdodge happy people. Plus it adds in dr. mario's vertical recovery.
Jabs are great, jab into grab is great or double jab -> usmash if you catch an airborn opponent.
Edgeguarding with him takes practise since you NEED to use the walljump. Stages like omega dreamland or yi are nice stages to edgeguard effectively because of the walls below the stage but stages without walls like bf reduce his edgeguard ability
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The only downfall dr mario has is his below avarage recovery, the thing I listed above and the lack of range against some characters. But he's a very very solid mid imo and really fun to play. Plus the most important thing for me is that dr mario has NO trouble killing. A lot of characters struggle with it in this game but it's one of doc's strongest points imo.
(I'm on my phone so excuse me for any typos XD).