I've seen quite allot of movies and TV-shows as of late so I should be able to drum up movies that come to mind. I find they are generally hard to find since there is not allot of them that come up, and if they do, its sort of a niche type of movie, except for Joker.
I'm thinking Split (2016) could have a sick portrayal of a incel - that's more mentalcel, and I'm referring to the character Kevin Wendel Crumb - the key personality that was abused by his mother but comes out when there is a connection with one of the girls he kidnapped who understands him. Not sure how much of a discussion can be on that. I went to the cinema to see that (was packed), and was riveted such a movie was played on a big screen like that, just felt it took allot of social taboo risks on that.
There is another movie called "Under the Skin" (2013). This is perfect for the incel idea. This lady is virtually stalking men, including one incel guy (spoiler alert) that she allowed to get away from her contraption. I must have re-watched this one 5 times. While may not identify with the ugly guy on there, I liked the way she seduced him and gained his trust and tricked him to go to her house. Maybe a case of MTGOW here.
I'm also thinking Table 19 (2017) - which is arguably a modern day re-telling of Breakfast Club (1985), has some real "incels" on that table.
There are not that many "incel" movies out there to go with the actors that sell the role convincingly, but this would be one of them.
Some 80s movies were nice like "Weird Science" (1985) where two incel high-school dudes computer generate a woman and one of them is antagonized by their chad-bully brother, but then again, they may be too young for an older incel crowd to identify with them -- sort of more in the proto-incel category with the 80s cheesy movies.
If anything comes to mind I'll post it up here. Of course you can probably google or find them out somewhere, and in truth, most of these movies I may like to see Scarlett Johanasson naked and like the cinematography and sound, or may find some other aesthetical aspect of the movie appealing, or I might like the director (ie. M. Night. Shyamalan is a great director and I've seen almost all his movies in cinema) rather than being chosen directly because they represent some incel aspect -- normally, within the movie hobby, these aspects are incidental and think they all have great ratings.