I can do at most 17 or 18 enemies per battle. What should I repeat to maximise kills?
you do not need to kill enemies for the challenge, you just need high amount of crits
I’m doing the 5000 kills in a week challenge.
I think the fastest way is just raiding in invasion breakers
Neither raiding nor Invasion count towards the challenge.
I finished that challenge about 2.5 years ago, and while I don’t remember with any certainly what I did to complete it, I think I just skipped raiding for most of the week and kept grinding away at it. Sorry I can’t be of more help.
If it’s about “Crit Crazy” challenge, quick fighting on breakers does count. This is how I completed that challenge on the first day.
Is there any stage in particular with a lot of mooks I can screenwipe using Mulan or Ian?
I think all Campaign stages, after the first few chapters, have the same number of enemies; ditto on the Team Trials and the Port difficulties. Although it may be possible that summoned allies, like Sven and Rajah, would count towards the total.