I'm trying to make a skill in rmxp which takes one enemy out of battle.

Which means that the enemy can not attack or be attacked for one turn.

Could someone please help me on this?

Try making a state change effect, which makes it so the target can't move, then set its defences and whatnot. Maybe make magic and physical defences like, double, and set evade to 100?

Stop trying to make anything Custom. Look at the Default skills and use/see all of them figure out and how/why they work that way.

Play with the default skills first before going any farther, it will help you learn how skill can be used and work.

Good Luck~

I'm afraid that doesn't work. because when I set evade to 100, the enemy can still be hit by skills with Eva_F = 0
And it doesn't matter how high the characters defense becomes. Because there is a mininal damage of 1.