DC has something which Marvel doesn't has, a standalone Film for its antagonist, The Joker. Joker doesn't has any superpowers like Thanos or any other typical supernatural powers which villains generally do but still he is one of the most fearful villain and certainly the most famous and bankable of all. But Why ?
The answer of this question is simple, its because we can relate to this character, a common man can understand his struggle and the viewpoint he is having, but that doesn't mean that I am glorifying his actions and violence is the never the way to justify something. Joaquin phoenix reprising the role which Heath Ledger made it a benchmark to beat in any negative role which I won't say Joaquin beat it but surely it was in par with Heath Ledger, both roles were amazing in their own way and was well done justice to the Joker.
So coming back to the point, why is Joker the most unique and fearful villain which has ever have been created, see the simple fact is that no one could understand him, he was submissive and had to go through a lot of mental torture which ultimately led to his deteriorating mental health, yes the term Mental Health which society doesn't care about it or pretends to ignore it, it is because it isn't a visible problem and importantly its more sensitive and bigger epidemic than any other physical health problems. Its a Silent killer and can make a person hostile sometimes but not every time which is in the case of Joker so yes in reality people like Joker can exist, a very good example can be of all the serial killers. It is in fact frightening that people like Joker can exist in our daily lives but not Thanos so yes, that is why Joker is the most realistic villain which has been ever been created.
So Joker being a terrific villain and Interesting to watch has more to offer than just being an Antagonist of a Film, it did deserve a standalone film and I am happy it exists now because behind every violent person be it in real life, there is always a reason behind it, which needs to be addressed you can't only blame them, seeing Joker in a different light was en-lighting and not just seeing as an evil character, again his violent actions are totally wrong but at the same time Mental Health Problems should be taken seriously or else there are always consequences which can impact lives of the people suffering and also the people around them. So yes, it doesn't matter if you are comic book fan or not, it's a must watch film, it is violent but has a lot to introspect about after watching it. For Comic Book Fans this Movie has already won an Award.