You can do a variety of natures, and can afford to Negative a Defensive Stat to make another stronger since he's a fast sweeper. I've used a Critical Strike Blaziken before.
Blaziken @ Scope Lens
Naive/Hasty/Naughty (whichever you want higher)
125 SPA/125 A the Rest Speed
Focus Energy
Slash
Blaze Kick
Earthquake
This gets you a decent variety of strong attacks, and with the High Crit Rate on Slash and Blaze Kick, and the added crit on the Scope lens and Focus Energy you'll be throwing Crits like no other, its a pretty unconvential and UU moveset, but it can be good.
Other choices are the Endure Reversal Build, and the Physical attack build