Baton Passed to Yusuke and used the severe damage skill which gets powered uo by Baton pass for 1.5, I believe. It's not much, but I'm proud of it as it was my first playthrough.

3000 cosmic flare with metatron on a bunch of enemies in shidos palace with concentrate and crit

Concentrate thunder reign with tarukaja and rakuna on some enraged mementos boss for like 3000 damage

2600 after charge up and power up from baton pass with Ann on some weak shadows in mementos.

I wanted that 999 hp damage trophy.

Huh, I'm not too far off. I thought I'd hear some stupidly high numbers.
Mine is a 3400 crit from a cerberus level 63 with oneshot kill, charge and attack master.
Kinda caught me off guard when I used that the first time in the final area and got a oneshot.. I wasn't used to killing anything very fast there xD