Sam already touched on this, but I just want to weigh in my thoughts on it. I think Grimer-Alola defiantly deserves to be raised up to A Rank it is a huge threat both defensively and offensively. Hard checking a lot of threats being used right now namely Abra and Gastly. On top of that it also blanket checks a ton of special attackers for example if it 1v1 against Life Orb Staryu and is above 70% health it actually wins that match up as Gunk + Shadow Sneak will get the kill, and this isn't taking into account its high chance of poison. It is hard to switch into as well having a very powerful Knock Off(the 30% chance to poison makes this even better) and nice neutral coverage when paired with Gunk Shot or poison Jab. Without a doubt is the best Pursuit trapper the tier has to offer taking little damage from coverage moves of Psychic and Ghost-Types outside of Hidden power Ground thanks to it's poison typing. All this makes it a valuable and splashable member to offensive teams, when paired with set-up Pokemon like Scraggy and Tirtouga due to the ease of which it breaks Abras focus Sash, just a great Pokemon that I feel deserves a rise.