Everyone has that one character they just can't help but dislike, regardless of if they have any reason to or not. For Dashie, it's Donkey Kong. For Jackscepticeye, iirc it's the kid riding in the back of the bike in Happy Wheels supposedly, which he dubbed Billy. For me? It's Wario. I have a love hate relationship with that one as I currently like absolutely nothing about him, and I never did like him. And yet, despite everything I dislike about him, I have fun playing as him in Smash and Mario Kart 8. In fact, he ironically ended up as my most used character in Mario Kart 8.
For me, it is Hawlucha because he is just ugly. I kind of like his shiny, but his voice in the anime was so annoying.
Colette Brunel, from Tales of Symphonia. Which is shocking because she's arguably the most important character in the game, but her personality and actions throughout the entire game just rub me the wrong way. It's one of the reasons I don't get Colloyd-shippers; just because they're childhood friends, and is one of only two friends Lloyd had growing up, doesn't mean they are OTP. Colette lies to him frequently, hides her true feelings more often than is healthy, and it all just gets swept under the rug because she's cute and needs to be protected and stuff. While she is not the MOST hated character ever (that belongs to Cowmilla and the rest of the Fire Emblem: Fates cast), she pops into my mind first because I *LOVE* Tales of Symphonia.
...Moneybags, the gem-hoarding bear from the Spyro series. Even Spyro himself gets fed up with him very quickly. He's a character I simply love to hate.
King K Rool from Donkey Kong. I always hated fighting him as an end game boss with his cheap tactics...
Mettaton from Undertale. The hardcore Sans fans are bad enough, but I am surprised Mettaton is nearly as popular as he is. He is an egomaniac and kind of psychotic. A bit too obnoxious.
It is hard for me to pick a single character since I don't really dislike any character from any game but I would have to say Bayonetta.....her physical appearance is just disturbing to me, need I say more?
I was never a big fan of Wario. Waluigi is cool, but Wario? Ehh... Princess Peach isn't my favourite either. Outside of Mario, I'm not a big fan of Shadow the Hedgehog (too edgy), Rotom from SM (annoying), and Rabbids (for obvious reasons).
In the playthroughs I've watched of various video games, I think Emily from Until Dawn is on my list of most despised video game characters. She's snotty, obnoxious, and pretentious. She cares only for herself- always placing the blame on her boyfriend rather than taking a step back and reflecting on her own actions- which is something I absolutely cannot stand. Throughout the entire game she's selfish and thinks the entire world revolves around her. To be fair, most of the characters in that entire game are unbearable, but boy oh boy does Emily take the cake.