How much MATK needed...?

How much MATK is needed for an MD stormer to 1-hit kill corroded fighter and corroded knight in the side quest free from the infesters? (without using combo | Just pure storm skill) (take into account the guard as well) (you can also mention ele + ele%)

Thanks in advance!

 

Just a rough calculation
Corroded Fighter (lvl 70) HP is 5500, idk about MDEF or even resist lets say its 50 MDEF
Storm multiplier each hit is 2
Storm constant each hit is 80
element advantage multiplier is 1.25

(X - 50 +80) * 2 * 1.25 = 5500
(X + 30) * 2 * 1.25 = 5500
2.5X + 75 = 5500
2.5X = 5425
X = 5425/2.5 = 2170

so you need 2170 MATK to one hit Corroded fighter (lvl 70) with storm.

You can get 2.5k to make sure its 1 hit ko, magic stability max is only 90%

 

I'd like to remind that corroded knight has high guard rate. So you may take it into consideration in case you still want to be able to 1hk the knight.