It's calmed down over the years, but Daisuke (Davis) Motomiya from Digimon got a lot of unwarranted hate at times just for being a spastic kid who "replaced" Tai as the gogglehead, and it doesn't help that the
dub scriptwriters themselves didn't like Davis all that much. But I think majority of the hate in the fandom came from the T.K./Kari shippers, to be honest, since he was a "threat" to the ship.
But as much as I like Davis
now, this scene is just fucking glorious.
Honorable mention for Ash Ketchum (Pokemon) - He's both the most white knighted and the most a-logged.
Lol dear God is he ever. The shitstorm over him losing the Kalos League to Alain was the funniest shit to come from the fandom in years. (Alain was actually
praised as a character in the spin-off Mega Evolution specials even though he's a boring Gary Stu. Then he got A-logged
hard for beating Ash to the point I think some people took a look at Tobias from the Diamond and Pearl season and reevaluated what they thought of
him.)
EDIT: But honestly, Tracey got more A-logging than Ash did back in the day. You couldn't get anywhere near a Pokémon community for years without seeing/hearing someone bashing the poor guy just simply for existing. I feel like most of the hate stemmed from Cori Falls, though, given her large influence in the fandom.