DeGrey's thing is "Frametraps". A frametrap is a string of attacks with an intentionally left gap that will allow the opposing player to start an attack after blocking the first in the string, but your second attack will hit them before their attack comes out. Hitting an opponent during the startup of their attack causes a Counter Hit, which DeGrey specifically gets big bonuses off. For example, on counter hit his bA ground punch will launch the opponent, and you can combo using fA cancelled into BB for 4 damage. BB on counter hit will cause the opponent to bounce off the wall, and midscreen you can then get another BB for 4 damage as well. DeGrey is the only character whose counter hits have special properties.
Note that frame traps fail if the opponent uses an invincible reversal in between your string, in which case you'll get counter hit instead (although they will not get any bonus off of this). If they're not mashing the reversal from the start, do a string a couple of times to condition them that it is a frametrap, in which case they might try the reversal. Block it instead of doing your string and punish. If they start blocking your frame trap instead, you can try for a throw.