kill 4 boss's guards challenge for level 5 operators.... how?

[Smoochy]

how do i kill the boss? i assume hes the dude in the red circle at the start? then when you get close he seems to move to a yellow circle. i kill him and all his guards but this doesnt seem to count for the level 5 challenge all operators have. help! im doing this solo que too so its not always easy going up against 3 haha

[Eudae]

Anyone figure this out?

[Hydro]

On layali, the boss reis is accompanied by 5 guards.
They count towards the mission completion. However, I recommend you do the other mission as you only need 3 for the next operator level and you’re offered 5 missions