How much can EV training increase a Pokémon's stat?

Question

So I'm using an Unfezant with Super Luck and I want to combo it with Air Cutter. However its SAtk is much lower than its Atk.
Can EV training actually help me balance the difference?

Answer 1

No.

An Unfezant with a neutral nature and 252 EVs on Special Attack at Level 100 will have a Special Attack stat of 229. Wit a positive nature, that becomes 251.
Without any EVs onto Unfezant's attack stat, Unfezant's attack is 266. This is higher than Unfezant's maxed out Special Attack
The only case where Unfezant's attack would be lower would be if it had a Nature which decreased Attack or it lacked IVs on its Attack

In contrast, an Unfezant with a positive nature and 252 EVS on Attack at Level 100 will have a very respectable attack stat of 361.

Physical Unfezant will basically always be stronger than Special

Answer 2

Well ok then if you EV train your unfezant fully with 252 EVs then at level 100 his special attack would be 63 stats higher.But does your unfezant have a hindering nature or something like that? (i it does breed another)