I've put together a shortcut to coup de grace for the kids. Not sure if there's another build like this.
How it works: You designate a Stunning Fist with your Snake Fang, and Dastardly Finish the following round.
Let me know if I missed anything.
Human
Rogue Variant Multiclass (Unchained)
Snakebite Striker
1. Sneak Attack 1d6, Weapon Focus, Enforcer
2. Improved Feint
3. Trap-finding
4.
5. Snake Style, Dazzling Display
6. Sneak Attack 2d6
7. Sneak Attack* 3d6
8. Stunning Fist
9. Shatter Defences
10. Sneak Attack 4d6
Fighter
1. Sneak Attack* 5d6, Evasion, Dastardly Finish
Master of Many Styles
1. Snake Fang
Let me just clarify that you can indeed get Snake Fang earlier, and Dastardly Finish by level 11, but Enforcer and Shatter Defences are too good to pass up. It all goes together like peanut butter and jelly.