Alright, I'm here to drop a gem of a mon that I've discovered.
Articuno from unranked to C
Articuno, with Focus Sash, presents one of the most interesting twists that the meta has seen for a while-a guaranteed accuracy OHKO move. With a Lock-On+Sheer Cold set, Articuno can drop a reliable OHKO on any Pokemon that it faces that doesn't also hold a Focus Sash or has sturdy. This can present a massive threat to many Pokemon. For example:
MegaRay vs Articuno:
T1:Megaray Dragon Dance Articuno Lock On
T2 Megaray Dragon Ascent-Articuno holds on using it's Focus Sash-Articuno Sheer Cold OHKO
Arceus vs Articuno
T1: Arceus Swords Dance Articuno Lock On
T2 Arceus Extremespeed-Articuno holds on using it's Focus Sash-Articuno Sheer Cold OHKO
As can be seen, Articuno requires effective hazard control and a degree of prediction, but the sorts of threats it presents move than makes up for these weaknesses, at least enough to justify it a ranking in C.
Call it a gimmick, call it bad, just remember the sort of threats that it could deliver to the meta given the opportunity.