Critical Hit Achievements

[IvanForever]

I am implementing in-game Achievements (e.g., the ones like Steam Achievements), but haven't been able to figure things out for the Critical Hit ones I want; this is something I've been stuck with for a long time.

I want to make these Achievements possible:

1. when the player lands a Critical Hit damage onto an enemy during battle;
2. when the player lands a Critical Hit damage to three enemies or "field of area" during battle;
3. when the player lands a Critical Hit damage after a particular item is used;
4. when the player lands a Critical Hit damage using a specific skill, and;
5. when the player lands a Critical Hit damage with a particular party member (and/or with that character's particular skill).

I was thinking perhaps there is a way with switches or variables that can help identify when the requirements for an Achievement is fulfilled, yet I am not exactly sure how to have these recorded during battle, especially right when a Critical Hit occurs. Hope there are people here who can provide me solution(s).