Charge a either one of the Kicks, and then release
There are 4 levels of drop kick
lvl 1: 100 damage
lvl 2: 150 damage
lvl 3: 150 damage, the screen shakes and it juggles higher and has better combo follow ups
lvl 4: 250, screen shakes more violently, if it hits mid screen it will knock back full screen, in the corner is has better combo follow ups
The different levels are achieved by holding the the button down for longer durations with higher levels requiring longer periods of charge time respectively.
While the game simply has it written for the player that the kick must be charged for 24 seconds, I stead will provide a measurement using the "in game" clock which will help you know which level of drop kick you have after any arbitrary amount of time charging.
A very important thing to remember is that Drop Kicks can begin their charge before the match begins. By having the button pressed and held during the, "ready" & "go" portion of the fight, you will have a level 1 drop kick charged the moment the fight begins.
level 1 and level 2 have no important difference besides the damage, level 2, as far as I know, does not yield any better position or give better combo potential, for this reason I have not bothered deciphering it's charge timing.
Level 3 and 4 on the other hand are more important via their combo yeild.
We'll begin by considering the pregame charge timing and then discuss the time required to charge either kick from a starting point within the match.
From holding the kick before the beginning of the match using a "60 second clock" you will have a lvl 3 drop kick charged by 51 second. The timing is very precise and assuming an "in the middle of the second" release and not an instant... therefore 50 seconds would be the 100% guarantee.
From the same starting point of charge, Raiden will have a level 4 drop kick by 47 seconds, 46 for sure.
Now that we've discussed the pregame charge beginning point lets discuss a charge time which hypothetically beings mid match, for this example lets use the 50 second mark.
Level 3 drop kicks take 12~13 seconds of charge time and level 4 take 16~17.
If you begin charging at the 50 second mark, Raiden will have a level 3 drop kick by 38 seconds, 37 for sure
From the same starting point, Raiden will have a level 4 drop kick by 34 seconds, 33 for sure.
"gen" like the character