I'd like to nominate Breloom for A- Rank.
Breloom, from what I've seen, is an excellent choice for this metagame. The meta revolves around Knock Off, and to a slightly lesser extent dark types, which is, put simply, the wet dream of a fighting type that doesn't care all too much about losing its item and is already solid in its own right. Breloom is just this kind of pokemon. It can tank hits from massive threats like Crawdaunt and Bisharp, and it beats 3/4 of the S Rank 'mon 1v1. Even Lando can't switch on Loom, lest it get smacked with Rock Tomb then outsped and KO'd after rocks on the next turn. In addition to this, a massive amount of Megas give Loom serious trouble, so in the No Mega environment it's lost a great many of its checks/counters: MVenu, Both Zards, MZam, MAlt, MGross, MGarde, MGallade, MPinsir, MLatias... the list goes on.
Breloom's rather hard to come by typing of Grass/Fighting provides some key resistances to Water, Ground, Electric, Stealth Rock, and most notably Dark, and therefore Knock Off. Unlike its Grass/Fighting counterpart (Chesnaught), Breloom has access to the oh-so coveted Spore, a massive attack stat that allows it to avoid being as passive as Ches, and two fantastic abilities in Poison Heal and Technician. This lets it run a multitude of sets: On offensive sets, Focus Sash and Life Orb are both solid items that provide different benefits: Sash allows it to beat stuff like Talonflame that would normally send it crying to its mother provided its got some spin/defog support, while a Life Orb makes Breloom's already strong priority in Mach Punch sting even more. Spore + 3 Attacks is an absolutely amazing set, but SD also seems like it could punch some serious holes in certain teams, or clean up late game with boosted Mach Punches. For something more defensive, a Poison Heal set can make Breloom a pretty solid tank, though I have not used this set enough in the No Mega meta to really go in-depth on it.
Overall, though, I think Loom fits in much better with the likes of Chesnaught and Jirachi in A- than it does with Hydreigon and Dragalge in B+.