Soldier is easily the most unbalanced class in Team Fortress 2. He has the second highest health in the game (200hp), potentially the greatest mobility (rocket jumping), splash damage that makes up for sloppy aim, three self healing weapons (each having separate equip regions), and I think a few more things I can't think of right now.
The Borderlands franchise has a few enemy types that are extremely poorly designed and just plain not fun to play against (Rabid enemies, Suicidal enemies, Enemies that's corpses explode apon death, etc...).
I find NPC dialog in Undertale to be too long and boring. I realize Toby wanted to tell a story through character dialog and some observations, but I feel like he could've told it a lot quicker and simpler so I didn't have to read seven full paragraphs of dialog from several NPCs just to understand a story as fairly simple as "Humans and Monsters fought in war. The Humans won and the Monsters got locked away underground."