In mid/late game, digivolve [BT2-041] ShineGreymon once you have enough tamers on the field. Typically you would want to use ShineGreymon’s effect to remove your opponent’s strongest digimon: assuming at 12000 DP would require at least 3 tamers on your field. In addition, you should also have <SecurityAttack+1> if you have inherited from RizeGreymon, and with +1000 DP for each tamer you have, allowing you to very effectively attack your opponent’s security pile.
In your subsequent turns, the game will very quickly shape to your favour as you continue to build your tamer pool and play a second ShineGreymon.