While I try not to use the same one all the time, I'd say my Arcanine and Toxtricity get used most in high-level raids, while Inteleon plows through lower-level raids.
Additionally, as none of my party could beat Gigantamax Snorlax in a solo raid, and no one was joining me online, I desperately took my Scraggy and fed him doping candy until he was a level 100 Scrafty. And it still took me half a dozen tries to actually catch the Snorlax (as irony would have it, the day after I caught 3 of them from other people's raids with no trouble at all). Scrafty subsequently became my last resort option for really tough raids: he's strong, very durable and has Shed Skin so he heals statuses by himself, which is very useful in a high-level Max Raid. Equip him with a healing berry and he can last out a 5 star raid, no doubt about it.
Small anecdote: one time during New Year's shiny Magicarp event, I was part of an all-Toxtricity raid. Only one person had brought a Low Key form, and they all played their electric guitar chests at the giant flopping fish.
You know, with anything other than Pokémon that would have been a really strange sentence.