Even though I am hating to admit it, but Pit doesn't like Kirby so much, and sometimes Jiggs, ugh...
I assume Pit does do really well against large heavy chars.
That would be DK, Bowser, Dedede, Wario, sometimes vs Snake, and maybe Ganon.
Basically Pit has an F-throw chaingrab (capped at about 40-50% depending on weight and DI) that works well against large heavy chars, especially DK, Bowser, and Ganon, then Snake... Dedede and Wario seem kinda floaty and have a better chance at escaping it.
In addition, Pit's N-air is really good against large chars. For Bowser and DK, he can use Mirror Shield to gimp their limited recoveries. As for the other mentioned chars, arrows just to stop their jumps when trying to recover.
However, Pit's Ledgecamp + Edgeguarding + Gimping capabilities (Chaingrab too) make him very brutal against DK and Bowser, maybe Ganon. As for Dedede, if he didnt have that chaingrab and long range to save him (Dedede is also floaty and can avoid Pit's CG easier than other heavies can)... but that doesnt mean that Pit cant take him down with pressure. Snake suffers the same from Pit's pressuring ability.