i think the fact that anti-ban people are even proposing things like arcanine in the first place to check it already speaks for itself how overwhelming it is
imho if kangaskhan didn't have either pup or sucker punch it'd be a lot more manageable, probably even not banned.
mk really only has 1 pokemon that counters it on a somewhat reliable basis which also results in a gigantic fuckton of loss of momentum for the opponent. you can support mk with strong knock off users (land-t, deoxys-d/s and weavile comes to mind) to remove scarfs and helmets. on the basis of helmets: just a piece of anecdotal evidence that may not apply to all: i haven't seen a single pokemon run helmet until after mk started running rampant across the entire tier, and even then it's still not that difficult to check pokemon with helmet. helmet also prevents pokemon from running other things that really benefit it more (ferrothorn definitely appreciates leftovers for some extra flexibility, not helmet and forced leech seed just to check a fucking kangaroo).
FadedChameleon trevenant dies to crunch
+1 252+ Atk Parental Bond Mega Kangaskhan Crunch vs. 252 HP / 252+ Def Trevenant: 357-423 (95.4 - 113.1%) -- 75% chance to OHKO
(357, 363, 366, 372, 375, 378, 384, 387, 393, 396, 399, 405, 408, 414, 417, 423)
above calc is if trevenant switches in on scrappy PUP
252+ Atk Parental Bond Mega Kangaskhan Crunch vs. 252 HP / 252+ Def Trevenant: 240-285 (64.1 - 76.2%) -- guaranteed 2HKO
(240, 243, 246, 249, 252, 255, 258, 261, 264, 267, 270, 273, 276, 279, 282, 285)
still half-dead
also standard never runs fake out, the standard is pup/sucker punch/return/crunch, EQ or fire punch
also ffs just because something is countered by something doesn't mean it's not broken, or something lacks a counter doesnt mean its broken either. gen5 hydreigon is a good example of something without a counter. definitely not broken, and was on danger of slipping to uu at the end of gen5 along with haxorus. kyogre is countered by shedinja. kyogre for ou pls. really, mk's ability to steamroll teams fairly easily is really telling. the best 'check' to it is wearing it down with random shit + rocky helmet, then sending in talonflame to suicide in its face. and you can still switch out. you need two, maybe even three pokemon just to check mk. how the fuck is that not ridiculous? for one pokemon you get to kill off two of your opponent's pokemon (sacrificial helmetmon, talonflame if its going into rocks). fuck no pls, ban