This is available in the first fight. Use all gadgets by doubling tapping their number.
1--Batarang, essentially.
2--Batclaw, but Robin launches towards the enemy instead of pulling the enemy to him.
3--Explosive Gel, might need to hit an enemy.
4--Snap Flash, an enemy must be nearby.
5--Bullet shield. Doubletap to hit an enemy with it. You need to connect or it won't count.
Copied from Trueachievements.