Question

Can I use last resort if it's the only move on my Pokemon?

Answer 1

No, you can't. The move will fail.

Last Resort inflicts damage and has no secondary effect. However, it cannot be used until all other moves that the user knows have been fully executed, at least once, during the battle.

>This counter resets if the user switches out, faints, or the battle ends. Last Resort will fail if it is the only move the user knows.

-Bulbapedia

Comments

The way Last Resort is usually used is along with just Fake Out. Although in actual competitive, don't expect it to be of any use.

Answer 2

Last resort will fail if it is the only move the user knows
-Bulbapedia

Comments

Too slow again -_-