Muppets who cant resign.

I'm not saying every move is perfect, or indeed a good move, but when the last move was played we both had 17 minutes on the clock. I resigned over 5 minutes later

The game for White was lost.

There are two ways to cheat and winning on time like this is one of them.

Play out, report, block.

If you resign such games, do you think your opponent will stop doing it?

On the contrary, you only encouraged him to keep doing it. When something like this happens it’s a good idea to sit back and relax, doing something else while you wait for the opponent’s time to run out. And then block that player so you never see them again. But it’s definitely not cheating, you gave them the win by resigning in a won position.

25/10 is a long game. You could reduce the damage with somewhat shorter games, 15/10 or 25/0. It's unfortubate but this phenomenon discourages longer time controls.

Simply do not play long games if you do not have patience to wait.Or what above was said: do something else while opponent's clock is running down.Eat a sandwich or watch a youtube video :)

If you're willing to lose why not just start a new game or go do something else and let his time run out? The worst that can happen is that he'll move and your time will expire. What's the point of resigning?
It's not cheating to use whatever time is still on the clock. You both agreed to play with that time limit.

There should be a way to report this while the game still is going on, so the system could declare the winner and the player banned altogether.

Wtf is this discussion? Everybody may take as much time as the Game allows. I also got flamed while i‘ve had a long think. This is simply rediclious. Either play Blitz or go afk/ resign if you have not enough patience. When i start a classical Match i make sure that i have at least half an hour of time for playing it.