Alolan Marowak -> B-
I think Marowak is being slept on super hard. Virtually nothing resists its stabs, and the few dark types that do get crushed by superpower/bonemerang. The ability to stop all relevant eletric types minus some like knock off thundy caliber shit is awesome. It has just enough bulk to take strong neutral hits like:
252 SpA Tapu Lele Psychic vs. 248 HP / 8 SpD Marowak-Alola in Psychic Terrain: 264-312 (81.7 - 96.5%) -- guaranteed 2HKO
Meaning its not too frail to be deadweight against offense. It also has an awesome matchup against stall with the following two calcs:
252+ Atk Thick Club Marowak-Alola Shadow Bone vs. 252 HP / 252+ Def Quagsire: 177-208 (44.9 - 52.7%) -- 25.8% chance to 2HKO after Stealth Rock and Leftovers recovery
+2 252+ Atk Thick Club Marowak-Alola Shadow Bone vs. 252 HP / 192+ Def Toxapex: 244-288 (80.2 - 94.7%) -- 50% chance to OHKO after Stealth Rock
Meaning after a swords dance, if you have hazards up and just a bit of chip, your opponent is in trouble. But what I think what really puts it over the top is how awesome its defensive typing is, allowing it to switch in to tons of relevant stuff, even beyond electrics, like clefable, ferrothorn, non dark move kartana, scizor and magearna, and immediately can start blowing holes for your sweepers. The fact that it has actual defensive utility keeps it relevant with blace around
The following replay shows it doing some work and really highlights the synergy with sleep powder tangrowth. I also really love the support it gives hawlucha in softening up things like lando for a potential sweep.
https://replay.pokemonshowdown.com/gen7ou-669099284