Before you start the game, equip the coin gun called 'Justice' (extra ranged attack helps with this) and the passive skill Counterattack . When you reach Stonebat in Jura's Requiem, don't trans and use Counterattack to push Stonebat against a wall (not a rock column and this is harder to do). Once he can be pushed back no more, let him attack you so you use Counterattack and fling him into the air. While he's in the air / starting to get up again, use Justice. For a normal Counterattack, only place two orbs down at a time and when Stonebat stands up again, he will instantly lose a lot of damage. If your Counterattack was critical, place three orbs. I managed to deal over 2.4k damage in a split second by doing this. Repeat for a fast kill.
Important notes:
-If he doesn't make contact with the orbs, move your position. This happened to me, so I moved left a bit while still facing him and then it worked.
-Pick up every 'Recharge' you see to increase the amount of orbs you can place so you don't run out when you try to kill him, and because they eventually disappear.
-Don't waste your ammunition shooting at anything else other than Stonebat if you use this tactic.