Here's an interesting question I came up with after going through some Fakémon designs. Are there any Pokémon that gross you out just by looking at them, or would do so if they existed in real life?
I have a lot of examples, but the Pokémon I find most disgusting at the moment are Dewpider and Araquanid. I don't particularly hate or fear spiders, but both their normal and Shiny forms come in... sorta radioactive colors, which are an instant turn-off for me. Their realistic movement when chasing you in the overworld in Sw/Sh absolutely doesn't help... and neither does the fact that the water they use for their bubble could have literally anywhere. A close contender would be Jynx; controversies aside, her purple skin suggests untreated frostbite, which combined with her resemblance to a human is just... egh.
Based on your descriptions, it sounds more like Pokémon that you find unsettling rather than gross. Is that what you mean, or do you literally mean gross? If so, then I have contenders that definitely actually gross me out. lol
Gloom and Vileplume – Gloom is constantly drooling and the Pokédex entries say that Gloom's drool smells horrible, which is gross. As for Vileplume, even though it can learn Sweet Scent, the Pokédex entries say that Vileplume's petal really stinks. Other than knowing how they smell, I am not disgusted by Vileplume in any other way because it's cute. If I had a Gloom though, I would be wiping its mouth pretty often. Oddish and Bellossom are sparred from being gross. Lol Good on them.
Grimer and Muk – They're literally comprised of sludge from raw sewage and really stink according to most of its Pokédex entries. If Grimer and Muk were real, honestly, I'd be terrified of them. Imagine them rising out your toilet drain while you're using it. omg
Gulpin and Swalot – They're basically living, sentient stomachs that can eat almost anything, According to their Pokédex entries, after they eat, they release a lot of toxic gases as they digest their food, which basically means they likely fart and burp all the time, which I'm sure really stinks. I'd be terrified of them if they were real as well because they're definitely capable of swallowing me whole!
Koffing and Weezing – They are Pokémon that constantly produce toxic, poisonous gases out their bodies naturally. The Pokédex entries also say that the gases stink too. I imagine that Koffing and Weezing smell like farts all the time. They also come in your house if its unclean to take in the fumes of your kitchen garbage.
Lickitung and Lickilicky – According to the Pokédex entries, they would lick anything to clean it, but apparently, whatever they lick stinks really bad because their tongues stink. Imagine watching your Lickitung or Lickilicky cleaning your toilet with its tongue. Gross!
Stunky and Skuntank – Pokémon based on skunks definitely stink and they even fart in their cries. I can't imagine how bad they smell. You can't smell Skuntank without stank and stank is right!
Trubbish and Garbodor – Obviously, Pokémon literally based upon trash would be gross. Imagine the garbage that you're about to take out coming to life.