critical-hit-levels

An attack has chance to do a critical hit which multiplies the damage done, with chances to do more damage rarely:
Example of such system:
5% chance of Critical Hit level 1:x2 damage
2.5% chance of Critical Hit level 2:x3 damage
1% chance of Critical Hit level 3 :x4 damage
0.5% chance of Critical Hit level 4 :x5 damage