The points Faerie and Archeo made are both good ones but the thing with Maple is that after they nerfed her consume ability and added the piercing ability none of her
individual abilities are actually broken. The reason why Maple is so OP is because she has so many different unique abilities that give her more options than most other players and that she keeps coming up with new and creative methods to combine her and her companions skills in order to pull off stuff that is basically WTF.
First, with the piercing ability there are plenty of attacks that can still ignore some of her defense and beneath that her HP pool is actually quite small.
Second, since consume is limited to only a few times per day she has to be careful with it and since her MP pool is also pretty small this limits how many times she can actually use certain abilities, such as Hydra to only a few times per day.
Third, none of her other skills, i.e. Abomination and Machine God in particular, are really all that game breaking, all they really do is give her added mobility and a way to attack.
In the final two episodes of S1 Maple had to pull out literally every single trick in her book to
just barely eke out a win against Payne (The blue swordsman guy). After that she was only able to do so much damage to other players by combining "Abomination" with her best friends skill "Kage Bunshin".
Finally, as for the Devs letting Maple keep all her abilities if you had paid attention in S1's final episode there wa a scene where the Devs were watching Maple's antics and they did consider nerfing her again but decided not to since apparently Maple is an extremely popular player to watch and the backlash could've been immense. Plus most of the higher tier players would hear about the big fight and decided that they want to take on the challenge of beating Maple for themselves which they couldn't do if the devs nerfed her
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. So all told the devs figured letting her be "More of a final boss than the actual final boss" was better for everyone, especially since it was helping to ship units of the game 😜.