The Deepest Cut

The Deepest Cut is an achievement/trophy in the first Bayonetta game that is unlocked by killing 20 enemies with Shuraba's Charge Modifier.

Description
"Kill 20 enemies using only Iai-Jutsu with Shuraba"

Guide
For this achievement you will need to perform Shuraba's Charge Modifier. To do this you must hold down. The longer it is held the more powerful the strike becomes, with it having three levels of power. You must perform this move to kill 20 enemies.

Witch Time will help you because then you have some extra time to charge the attack or to be able to put some distance between you and them.

Try using it on the weaker enemies, the stronger ones have enough health to not die from it. For a quick way to get it try to get a group of enemies, if there are any stronger ones then knock down their health quite a bit then try it.