Unsportsmanlike: let timer reach zero

there is this guy I played against, the moment he felt it's a lost game, he stopped playing and let the timer reach zero from 3min, on a 5min game
I reported for stalling...
Good. Just report them and move on with your life. Good you didn't post their username because that forums aren't a place to shame people like that.
When you report someone, chess.com looks into it and then decides what to do. Usually they begin with warnings, then temporary mutes and the more severe side could be a ban/closing their account.
If they also timeout of many games, show poor sportsmanship (such as letting their clock run out etc.), then they also get put into a different player pool with other poor sports. There is no way of seeing what player pool someone is a part of, but there is one player pool with poor sports (so they get paired against each other more often) and then the pool with the rest of us (so we are less likely to encounter people like this in our future games).
I had someone who was losing offer me a draw. I declined. He then said to either accept the draw or be prepared to stare at the screen for 8 minutes while the clock ran out.

Happens to me a lot. I play 30 minute or 15/10 games, and I always report my opponent and block them as well. In a lot of instances I get a message from the moderator(s) that they have looked into the report and modified my rating as a result. Quite frankly, it is so annoying that there should be some kind of shaming which allows the rest of us to refuse to play a consistent game staller/quitter. I have only "quit" one game, and that was because power went down. When it came back up, I immediately got on line, looked up my opponent, and sent a message explaining my problem and apologizing.

there is this guy I played against, the moment he felt it's a lost game, he stopped playing and let the timer reach zero from 3min, on a 5min game
I reported for stalling, then I checked, this guy been doing that on EVERY single game he is losing, and he is still playing like nothing happened
I have the account, but won't post it here, is there a way to make this stop, because a LOT of people are doing that, and it is the main reason I stopped playing 10min though I still have a lot to learn but I cannot afford staring at the screen for 10min just because a kid lost his queen .. hopefully a game master will see this
You have a point. I haven't seen this very often, but it happened on one of my games. I was one move away from checkmating my opponent, then he somehow disconnected and then the game auto-resigned.

I usually let it go when my opponent decides to stall out of spite, but there is nothing wrong with reporting them and blocking them if you wish.

I had someone who was losing offer me a draw. I declined. He then said to either accept the draw or be prepared to stare at the screen for 8 minutes while the clock ran out.
not cool of him
there is this guy I played against, the moment he felt it's a lost game, he stopped playing and let the timer reach zero from 3min, on a 5min game
I reported for stalling, then I checked, this guy been doing that on EVERY single game he is losing, and he is still playing like nothing happened
I have the account, but won't post it here, is there a way to make this stop, because a LOT of people are doing that, and it is the main reason I stopped playing 10min though I still have a lot to learn but I cannot afford staring at the screen for 10min just because a kid lost his queen .. hopefully a game master will see this