What makes Pokemon broken?
a combination of various factors.
for an offensive threat, your plan is to:
bring it in
set it up (if required)
kill your opponents mons
while your opponent tries to stop you
a pokemon is broken if it does all or many of these really well to the point where the entire game becomes about bringing it in / stopping it. so let's look at our currently broken mage:
1. it's very easy to bring in due to its incredible defensive typing and solid bulk
2. it has multiple options for setup. calm mind or iron def can make your opponents special/physical attacker a sitting duck. shift gear allows it to outspeed a lot of things in one click and draining is a ctrl Z on the damage done to it thus far. so setting it up is very easy. it also gets passive setup with its ability. one drawback is that stored power sets aren't putting much direct pressure until you set up
3. once set up, your opponent finds it increasingly tough to eat the snowballing stored powers, so you basically win
4. your opponent will attempt to foil your plans in various ways. either with direct counters or by crippling it with stuff like encore trick or priority.
mag matches up extremely well into this meta. direct counters are limited to steels, and your opponent doesn't know if you have aura sphere or not until its too late. if you do go down, you'll usually have at least traded, so mag basically always gets you a good return on investment. also you could run volt switch and just dip
for status, nothing bothers it except para, and it can just shift gear past the para and draining kiss away damage it took on any immobilised turns. it's annoying but not a death sentence. trick and encore work if you can get the mon in (Latios, sableye are weak to DK). priority is doing nothing.
there are ways around it but you need to plan in the builder itself.
Zucario however isn't consistently putting enough pressure once it's in to be broken, and it's paper thin too
but yeah barely disguised magearna rant over.
TLDR if a mon has many easy entry and exit points, easy to set up, and difficult to stop once up, to the point where the game warps around it, it's broken.
This comes about as a combination of complementary stats moves abilities typing and the metagame around it (potential counters, enablers)
