Kingdra can have the ability sniper so he must be able to learn at least one move with a high critical hit ratio because sniper increases the damage that critical hits do. So I'm just curious what he can learn.
I am sorry Mewderator but you are wrong. Kingdra can learn razor wind via breeding and that has a high critical hit ratio.
The only move it can learn that is a high critical hit ratio is Razor Wind, which isn't really a good choice because of low power and charging. An alternative to high critical hit ratio moves is a scope lens. Give a scope lens and there will be a 6.25% chance of a Critical hit. Teach it Focus Energy and give it a scope lens and you will have a nice 25% chance of an attack being a critical hit.