What moves boost a stat by three?

Question

Cotton Guard (3×defense) is the only one I know. Can your imagine a Pokemon with simple using that?

Answer 1

Only Cotton Guard (3 stages+ Defense) and Tail Glow (3 stages+ Sp. Atk) are able to do that.
I hope I helped!
Note that I put stages instead of times because each stage increases the stat 0.5 times.
Source: Here

Answer 2

So far, Cotton Guard and Tail Glow are the only moves that raise a stat by 3 stages. The only move that raises it more than that though it Belly Drum (maximum) so yeah, raising that many stages is rare. Cotton Guard has poor distribution and Tail Glow is almost exclusive to Manaphy.

Hope I helped!