Question

Is there a really fast Pokemon in Pokemon omega ruby that can learn toxic spikes and is good at wifi battling?

Answer 1

Tentacruel @ Black Sludge
Ability: Rain Dish
EVs: 252 HP / 32 Def / 224 SpD
Calm Nature
- Toxic Spikes
- Rapid Spin
- Scald
- Ice Beam

This is a good support setup for Tentacruel - perfect for Toxic Spikes. His SpD bulk makes him one of the only viable Pokemon to set up Toxic Spikes. Rapid Spin for set up coverage and Scald for damage output and 30% burn chance.

Comments

What about Roserade?

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I personally prefer Tentacruel but you can indeed have a Roserade just for spiking.

Roserade @ Life Orb
Ability: Natural Cure
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Toxic Spikes
- Sludge Bomb
- Giga Drain / Leaf Storm
- Hidden Power Fire / Rest / Sleep Powder

Answer 2

The Fastest would be Scolipede.
with 118 base speed and speed boost its nearly guarenteed to setup toxic spikes.

Scolipede@ Focus Sash
Speed Boost
252 speed 252 atk 4 hp
Toxic spikes
Protect
Poison Jab
Xscissors

This set allows it to setup spikes and then do some good damage(possibly sweep)
also you can replace something for Baton Pass and give a new poke some great speed if you prefer.