Help me pick a 6th Pokemon for my team?

[GiMYz]

I think that a set with Flare Blitz, Close Combat, Snarl and Protect can work well. I'm not an expert of Arcanine's EV spreads so i can't suggest one in particular, but your Suicune and M-Venusaur are bulky enough so you can also run an semi-offensive EV spread on Arcanine to get rid of Grass and Steel types as soon as possible.

about Hydreigon, you can run a Choice Scarf set or a Choice Specs one. This set outspeeds Adamant ScarfLand-T by one point, so that you can catch it before it goes for the U-Turn or Superpower. This set also survives a Jolly Garchomp Dragon Claw. Dark Pulse is important because of the flinch factor, since you will outspeed anything that is not under Tailwind (it is also a better way to deal with Rocky Helmet Cresselia)

Hydreigon @ Choice Scarf
Ability: Levitate
Level: 50
EVs: 44 HP / 36 Def / 220 SpA / 208 Spe
Modest Nature
- Earth Power
- Draco Meteor
- Dragon Pulse
- Dark Pulse


The Speed EVs of this set can also go in bulk if you are able to play with Hydreigon under Tailwind. Fire Blast is used on this set because of Choice Specs boost, which let you get a OHKO on M-Mawile (without Rain)

Hydreigon @ Choice Specs
Ability: Levitate
Level: 50
EVs: 44 HP / 36 Def / 252 SpA / 176 Spe
Modest Nature
- Earth Power
- Draco Meteor
- Fire Blast
- Dark Pulse