Frogadier has no switch-ins, it’s capable of easily OHKOing and outspeeding top threats like P-Groundon, and P-Kyogre. With just Life Orb; Hydro Pump, Dark Pulse, Grass Knot, and Ice Beam it’s capable of 2HKO-OHKOing most of the tier. Choice Scarf would allow it to out speed almost the entire meta, while still dealing a big amount of damage with just Dark Pulse or Grass Knot.
Porygon 2 will have outrageous bulk and power. With it’s z move, it’d be even more ridiculous. 
Magmar, Electabuzz, Magneton, Haunter and Kadabra have ridiculous power. They also have ways to guarantee at least one kill every game. Kadabra will disrupt any playstyle, most of all: stall. All of these threats also sit at decent speed tiers, especially Kadabra and Haunter. Magneton would eliminate all steels. 
Duosion has access to trick room, decent bulk, regenerator, and 250 Base Special Attack. It could easily hold colbur berry to deal with Yveltal if trick room is already up. It'll OHKO most threats, which is stupid broken. 
Rhydon and Boldore have ridiculous power and access to priority in accelrock. Rhydon also has ways to boost speed in rock polish, allowing it out speed many mons and 2HKO-OHKOing them. 
Doublade has ridiculous power and bulk. It'd be too much to take on after a swords dance. 
Roselia having spore and vast amount of power will force many 50/50s.