Fastest to get and does the job.
Aron has sturdy, which serves as a substitute for Focus Sash, and instead you can give it a Shell Bell and use F.E.A.R many times.
Aron @ Shell Bell
Any Nature (Perhaps a Speed or Defense/ Special Defense decreasing one?)
IVs: 0 Def, 0 SDef, 0 Spe
- Quick Attack
Rattata/Raticate is (I think) the original FEAR Pokemon.
But these are some other ones
There really isn't any "Best" FEAR Pokemon, it's just whatever works best for your team.
It depends on the generation which Pokemon is easiest to find. Gen V it's almost impossible to get the Pokemon I mentioned above before reaching the elite four, unless you can trade.
@ Focus Sash
* (and 2 filler moves/ it doesn't need other moves)
Starly's the one that I see the most, but tbh, any Pokemon that can learn Endeavour + a priority move will do equally as well.
List of FEAR Pokemon