It took ella to take him down, Cole and two other members of Ella's faction (not S.I.N. , don't confuse the two) did nothing but practially annoyed him and he was heavily weakened even when they all fought him (he had just lost his heart).
He was greviously injured when The Main Character decided to fight him plus he didn't even die, just incapacitated.
[just asked PP, Max power you can get is 359]
I think it's more than that. 363.
The highest MC can reach before evolving is 115.
73 up till the Mall (perhaps I will edit this post later to do a full breakdown)
10 (83) from horn
1 (84) from beating Laurie correctly
1 (85) from reaching day 89
1 (86) from beating Tiff correctly
1 (87) reaching day 95
1 (88) Laurie side quest
1 (89) Train with Michael side quest
1 (90) Random power up during Alice side quest
15 (105) final stretch before Diamond Battle
During diamond battle you have 2 options
Learn how light power works | +5 power / +3 skill (110)
Aglaecwif choose strength | Choose + 10 power (115)
So the highest power you can get before the latest update, is 115 + 200 from evolution = 315
The latest update can give you up to 48 power.
10 from training 1
3 from training 2
10 from asura
10 from not being detected during infiltration
10 from shopkeep monster item
5 from shopkeep monster item
So highest possible power after the latest update is 315 + 48 = 363