Yara_B:
I think what makes him unique is how well he is written and how he steals the show every time he shows up. The author made sure he was bad enough to where he wasn't liked but also good enough to where he can redeem himself. That's a good balance. For me personally, when a bad guy gets a good ass redemption arc, they are worth the hype and love.
TTJ was a good example of a character with a good redemption arc; in the novel, the drama made him too good. My all time favorite fictional is Mo Ran who is way worse than XL; he's a scoundrel, a dog, and extremely shameless but his redemption journey was one of the best thing I've ever read; opinions may differ since this is also a huge debate among 2ha fans and nonfans.
It's quite a common trope so it's not unique where the bad guy is redeemable and gets a redemption arc. But personally, I draw the line when this type of bad guys starts physically abusing someone for the wrong reasons and in unnecessary situations with some even to the point that they do it because they feel 'good' when they hurt someone.
LYF trope and ending reminds me of another drama that I can't recall the drama title of but the bad boy ML was physically abusive and reminds me a lot of XL, especially with how things ended in that drama where FL ended up with the green flag ML who she fell in love with and the bad boy ML died.
XL's case is sort of the same but he becomes more good than evil and self-sacrificing yet similarly, he kept pushing his own ambition (or in this case loyalty) till the end. Still what he did to Xiao Yao at the beginning was one of the, if not, the main reason why I never thought about jumping to his ship with Xiao Yao.
But I do agree that he was well-written just like all the other characters in LYF.