I mean the ones with the most Pokemon that can have them.
As of Generation 9, the three most common Abilities are Swift Swim (47), Sturdy (47), and Intimidate (46).
Honorable mentions are Keen Eye (43) and Levitate (41).
Source
Levitate (38) Gives full immunity to all Ground-type moves.
Swift Swim (38) Boosts the Pokémon's Speed in rain.
Chlorophyll (35) Boosts the Pokémon's Speed in sunshine.
Studry also comes close with an honorable mention of 32 pokemon.