You mean increase the "Accuracy"? Then yes obviously. Though first, their accuracy is increased by 1% for every level higher you are too them starting at 30% Source.
Some good ways to increase Acc for OHKO moves are:
- Pair in a double battle with a Pokemon with No-guard (Machamp/DW Golurk)
- Acc boosting moves (Hone-claws, and Coil)
- Evasion lowering moves (Defog)
Though be warned most of the time OHKO moves are banned from competitive play.