The reason Mal was so detrimental to tgt is because he is the personification of toxic masculinity and is a douchey boyfriend simply because his girlfriend is doing better without him (will get to that) and the worst part is that his actions were NEVER acknowledged as being toxic. Throughout the series, Mal is consistently shown to get angry and put down Alina for being herself - a powerful Grisha, who is literally trying to save the world! Perhaps it’s not as evident in Shadow and Bone (has his moments) and Ruin and Rising (where he goes through some redemption arc but I personally found it extremely dull and the ending of the books made me hate him even more) but Mal’s toxicity is very clearly evident in Siege and Storm even from the very beginning. A list from the toxic things Mal has done:

1. Yelled at Alina for daring to fit in and be happy in The Little Palace even though prior to that he had no problem ditching her - which could have been overlooked perhaps if it weren’t for his actions later on in the series (Shadow and Bone)

2. Is described as being really happy while Alina is clearly suffering by not using her powers (a recurring theme in the book) 

3. Gets angry at Alina whenever she is a powerful grisha (something she wanted to be and has stated multiple times in the book) and continuously puts her down and tries to make her a ‘commoner queen’ despite her CLEARLY not wanting it

4. Gets angry at Alina for wanting to save the world?????? Bc she isn’t paying enough attention to him

5. Cheats on her with Zoya because “she doesnt give him enough attention”

6. Disregards Alina’s trauma and gets angry that she flinched (this scene made me furious) 

7. Is excessively jealous and self-centered

8. Guilts Alina for being herself and powerful (will talk about this more later)

9. Is literally the reason Alina got her power ripped from her (will explain this point more later)

There are more points but this will drag out for too long if I point out every shitty thing Mal has done. The reason I have a huge problem with Mal is that his actions aren’t acknowledged as being gross and unhealthy like the Darkling’s were but instead Bardugo continued to push on the agenda that Mal was the good guy, even though really, he caused more problems for Alina. Mal is the typical white guy who gets threatened by his girlfriend having power which in our society mirrors the guys that get angry when their girlfriends get paid more and have a better job so they consistently put their girlfriends down and project their insecurities on them because of stupid patriarchal values that push for male superiority (excuse me while I go puke). He is emotionally abusive (constantly guilting and degrading her) and gets unreasonably angry when Alina is thriving and is just a jerk to everyone for no reason but the fact that he is insecure. The problem I have with Mal is that his actions are gross and very realistic and a genuine problem. Most of us have probably encountered a Mal in our lives (some have unfortunately even been in a relationship with a Mal) and that’s what makes me so angry about his toxicity not being called out by Bardugo because unlike Alina’s situation with the Darkling, her situation with Mal is much more common in today’s society. In fact because of this he is worse than the Darkling because even though the Darkling is the villain and irredeemable at least he encourages Alina to reach her full potential - something that Mal continuously wants to undermine. 

Now moving onto point 9: Mal being the reason Alina got her power unfairly ripped from her. While from one standpoint it could be argued that Alina got her power taken from her due to her greed, if you look into the ending slightly deeper, you would find it strange how Mal gets everything that he wants despite having to be dead??? And he magically comes back to life and gets his housewife (nothing against housewives but Alina never wanted to be one) and Alina loses everything she wanted to conform to Mal’s standards and dreams. To me, that ending is absolutely disgraceful, unfair and degrading because why is it that powerful women always get their power unfairly ripped from their grasp just to satisfy the wishes of certain toxic men? What kind of message is that giving? The thing about books is that they are powerful and could change the lives of a person, so when an author gives that type of ending and refuses to acknowledge the problematic actions of their own characters, it gives young girls a message that Mal’s behaviour is acceptable (which is not) and that as a girl she shouldn’t overpower/overachieve the man which is disgusting and a very real problem in today’s society.

In conclusion, the reason Mal is so detrimental in tgt is that his actions are very real and very unhealthy and they aren’t acknowledged and instead excused and glorified which is very concerning as it makes young people believe that type of behaviour is okay, when really it is not.

There are is another good take here.