The two we've seen kill both appear to have spent the years prior surviving in the fringes of criminal society while being used and abused and then were given sudden, godlike powers to get back in ways (tactile physical violence) that wouldn't be available to someone like them otherwise. They weren't normal girls prior due to circumstance and definitely aren't now. I wouldn't say they are boss level. Nothing they've done seems far beyond the levels of having a hit list, powers, with at least one of them with prior experience with organized crime structures she's probably trying to use. To me it feels like the early days of what someday could be a real boss.
The other two power users are entirely different. Having powers without that rage and drive seems to make their use of powers on the surface seem more playful and creative. Right out of the gate the younger sister was playful with hers and the older reserved. But how she manhandled the boy in the air with little consideration of him demonstrates it would be difficult to tell them no. They're like capricious new little gods between their ages and impulses. Not really much brains between them though. Just the origins of future dangerous people.