There are a few very high damage weapons that help. Those are low circulation, but there are players that rent them out, or if you know the right people, maybe you can borrow one. I know pokey477 used to rent them, either with a cash deposit to ensure he gets it back, or by joining his faction while you are using it. I don't know if he still does.
Dual SMGs, Merits maxed ( Crit, Str passive, SMGs) , on Vicodin and waiting for that for the special proc as it empties the whole clip in one go. I recommend buying losses. That way your energy usage is not a deciding factor and limiting your ability to obtain the merit. Good luck !