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Nightmare Fuel: Toriko
Tommyrod. Good God, what a monster The man is a walking insect nest, who can do some downright disgusting things with his bugs. And don't get started with his rows of razor sharp fangs
Grinpatch. Insect-emulating mutated abomination, with a taste for others' despair. And he means it literally. Only fails to be the most disgusting and nightmarish character in this manga due to being completely overshadowed by Tommyrod.
Zebra can make it sound like he's standing right behind you even when he's tens of kilometers away.
When the ancient Nitro first appears behind Komatsu. Nitros in general, being the inspiration for the GT Robots.
Losing a bet in the Underground VIP Area of Gourmet Casino means you will forget the taste of every food you have ever eaten.
The huge monster that represents the Four Beasts in the legends describing them is terrifying. The image of countless humans writhing in its jaws...
The ending to Chapter 208. Oh God, the ending. Mood Whiplash at its finest. Anymore would spoil. Turns out to be just a nightmare.
The Pierced Nitro in 222 and 223...
The Giant Parasite in 224. To quote Sunny: "GROOOOOOOOOAAAAAAAASSSSSSSS!!!!"
Toriko's state after his battle with Stayjun. Remember how he looked after battling Tommyrod, minus one arm and generally beat up and covered in his own blood? HE GOT OFF LIGHT THEN IN COMPARISON! After fighting Stayjun and managing to inflict a mortal wound with his Routine Energy, he's collapsed against a cliff...has only one arm left, is covered in burns and the blood is used as a censor for his worst injuries.
Just about everything about Joa. The fact that he can erase and replace a person's personality, that he can turn your best friends into your worst enemies, that he casually rides on a Phantom Beast with a Capture Level of 295, or that he apparently is even STRONGER than characters like Setsuno, who are very much regarded as the strongest fighters of the Human World. Oh, and he also won the Cooking Fest 200 years ago, and still managed to erase his name from history. Not to forget that he is in cahoots with the secret organization NEO, who seem to have their agents planted just about everywhere, implying that Joa may be one of the, if not THE, most knowledgeable characters in the series.
From episode 113, more Accidental Nightmare Fuel than not, the Zemen noodles sound remarkably like a human being when massaged, which is very surprising coming from a non sentient food