These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Smash Bros Lawl
Badass Decay: When Irate Gamer first appears, he trophies AVGN and summons the Game Genie to trophy the Nostalgia Critic as well. In his next appearance, he is shown running for his life and requiring assistance from Ganondorf.
Justified: He took the Nerd by surprise, and the Critic was arguably tired from the fight against the Nerd.
Game Breaker: Ib's moveset would be such if used in an actual game since it gives the player an absurd amount of field control. Chincherrinas even implemented a nerf in the video description based on one of the comments he received to delay the painting effects.
Tear Jerker: Nostalgia Critic, Tommy Wiseau, and Madotsuki mourning the loss of their loved ones from Real City is actually a little sad. The background music helps.
That One Boss: This is not a real game, but the way some bosses are presented give the impression of difficult bosses.
Game Genie appears to be these. He's only vulnerable without his ghostly tail, which disappears at random, whenever he's not using powerful explosion attacks. Even when he is vulnerable, he's trying to wallop you. And he's one of the first fights of the very second level.
Big Red. If he swallows you, it's an instant KO, but his open mouth takes up most of where you can hit him. He also has an attack where he tries to knock you closer to his mouth.
The Persian Messenger is always zipping across the screen. It's hard to see him coming, and you take damage for being in the way. He appears to only be vulnerable when he stops so that his horse may neigh, but this is a short window of opportunity that takes an amount of time to happen again.
The Woobie: Madotsuki, judging by her back story on her trophy.