Better yet:
*Move tutor for Pain Split on lvl 1 Pineco, or Nosepass; use their evolved forms for Toxic/Spikes Immunity.* Survive any attack with Sturdy, then Pain Split back to full health, while the foe loses about 50% max HP.
Rinse and repeat to stay alive forever. Pain Split can bypass Taunt, just be careful of them using Substitute.
*I chose moves that don't require level up (egg moves, TMs, and move tutor).
Pineco lvl 1 @ Lum Berry [For Burn, Toxic, Confusion]
Sturdy
Pain Split
Toxic Spikes
Stealth Rocks
Toxic
First let them attack you or Taunt you as you Pain Split back to full health and take away their HP by about 50%, then Toxic/Spikes them as you predict them try to switch. Pineco's advantage is being able to set up entry hazards as your foe realizes it cannot hurt him without using Toxic, W-o-w, Hail, or Leech Seed. By the time your foe switches in a status inducer, you will have at least 1 layer of 1 entry hazard up.
OR
Nosepass @ Leftovers [For Hail]
Sturdy
Taunt
Pain Split
Magic Coat
Toxic
Magic Coat works well on Nosepass to prevent Toxic, Burn, Leech Seed, etc. from causing indirect damage, and instead directing it back at the user. Another advantage of Nosepass is having Taunt, which forces foes to attack you, and prevents Roar or Whirlwind. Toxic is the only attack worth using since nothing besides Pain Split deals enough damage as you attempt to wear the foe down.