Two types of hits: normal and critical.
Every weapon has a "edge", a different way of making crits. (see also Dead Cells)
Edges are related to mechanics of the combat system, eg:
- Parrying,
- Backstabs,
- Dodging,
- Stuns,
- Headhshots.
Some enemies are vulnerable and/or immune to some edges. For instance, enemies with helmets could be immune to headshots, enemies with heavy weapons can't be parried, etc.
Enemies with armor can only be harmed with critical hits.
Some missions can constrain the player to a certain approach by giving or taking weapons away from them.
The player has quick and charged attacks. Some enemies can exploit this by interrupting the player's charged attacks with quick attacks. The player can exploit this by baiting the enenmy with a charged attack, interrupting it, and countering the enemy's quick attack.
More generally, the player should have several types of attacks, and enemies should have ways to anticipate / counter them.
Enemies should have different strategies (wait for player to attack, spam quick attacks, etc), and switch between strategies if the player beats them.