I've mained three classes: Scout, Pyro, and Sniper. The first one I mained was Sniper, but I got too good at landing headshots and people kept accusing me of hacking. Unwilling to take the verbal abuse anymore, I switched to maining Scout. This was back before a certain profane term started getting spread around about Scouts that starts with "Sc" and rhymes with "blunt" and "hunt" and "stunt". I got pretty good with Scout too using the Force a Nature, Cleaver, and Sandman combo. I was mostly satisfied with this for a while, but then I started getting really good at ambushing with Pyro and reflecting with airblast.
Unfortunately, the TF2 community is really unfair with their criticisms of using literally any Pyro weapon, so I got a lot of verbal abuse from people complaining about how bad or OP an equip or equip combo I had was. Even just going stock would get people complaining, so I started not playing Pyro as much.
These days I don't really consider any of the classes as my main, I just pick whatever I feel like I need to for the sake of progressing the match in my team's favor. I stay out of ranked competitive servers as a rule, I prefer the silliness of casual servers. I always have the most fun when I manage to find people to play with and against who can keep their chill and just want to have a good time. It doesn't matter who wins or loses as long as everyone has fun, there's no need to accuse someone of cheating or using a bad/unfair loadout just because things aren't going your way in casual. Especially since crying wolf too much can cause people to not take real cheaters seriously when called out.