Hmmm ... I've had a long think about this one & the most controversial one that comes to my mind would be "A Clockwork Orange (1971)". The main reason I think it could've benefited from the loss of the main character would be due to the fact that someone as unhinged as Alex would probably be at risk of some kind of mental trigger that sends him haywire & causes him to hurt or possibly kill someone. Also, his suicide could've indeed proven that the government-run facility had gone a step too far with their dangerous experimentation & his loss of life could have ensured the safety of all future prisoners who might hope to someday lessen their sentence by becoming human lab-rats (to potentially something far more deadly). As wrong as it may sound, Alex taking his own life could've been fated to happen for the good of others, (except they decided to film it the way it is now instead). Honestly, though ... I hope my post doesn't sound like I'm as crazy as all that! LOL.