When do you guys think that your opponent could be dishonest?

I am adressing to the people that have been through this situation when they suspect their opponent to be a cheater. What are the precise criterias that can make you believe such thing? I am asking you that because I just defeated a guy who was really playing like a begginner ( to be polite ) and blundering eveywhere, even though he was way higher rated than me. To have a more accurate idea of what i'm talking about, here is the game :

Here is his instant reaction after his crushing defeat :

The point is, I did'nt play a great game and I'm not really good either. I just exploited his lack of understanding of the chess fundamentals. Do you automatically think that your lower rated opponent uses an engine when he outplays you by a decent margin? In which cases do you "nose" cheating in your online games?

I think it has been pointed out that a lot of cheaters cheat because they think a lot of their opponents are cheating as well. I have never played a game where i thought my opponent was cheating and I think the best course of action is to just not worry about cheaters.

I don't think he played like a beginner - how many true beginners play d4 let alone the four pawns attack? - and I don't think its really true to say your opponent doesn't understand chess fundamentals. And given the quick engine analysis shows White was better on move 16, the defeat wasn't as crushing as you make it sound.

But of course his accusation of cheating was petty and silly, despite mistakes you played better overall and he lost.

Times I have been suspicious of cheating (more on than here but also here occasionally) are when an opponent plays a complex middle game very well and fast, taking ~5 seconds a move, and then continues to play out a totally and trivially won endgame at the same speed, whereas (IMO) genuinely strong players need to think in the middle game but can blast out easily won endgames at < 1 sec/move.

I am never suspicious. When I get rating points refunded, it alsways takes me by surprise.
Really ... during the game I only see that my position gets worse and worse. But it was me who made bad moves, and the same thing can happen against honestly playing human players. I don't have time to worry about cheaters.

Maybe he was just tired?? I know I am sometimes when I play.

Ok I generally hate those people that think they are really smart and judge through the situation without having a single clue of what is actually happening. First of all , he/she didn't play bad , YOU played good. And before even thinking about accusing someone of cheating or blindly public shaming a person in the forums , have you ever thought about considering what could be happening on the other side? I personally always play like that when I'm tired or stressed , who doesn't? He/She could be walking his dog while drinking coffee while playing you or having a shower or playing poker or even giving his dog a daily bath. Do you know what is happening on their side? Even if you do get to a point where you suspect an opponent of cheating or if they are accusing you , REPORT THEM. Don't public shame.

Thanks everyone for your enlightening answers, this was indeed quite disturbing to observ such a statement from a guy that didn't play a great game - even if the match was in fact pretty even at the beggining, thank you piscatorox for pointing this out. Still, we are far from this situation with Jan Gustafsson from chess24 that got completely torn apart by a random dude from out of nowhere ( ).

I really would have accepted his suspicions as a legitimate thought if I had been blitzing the middle game and going slow at the end. But here, this is just a classic case of sore behaviour. Maybe he his a child, also. I should have considered this possibility. Anyway I'm glad that this confusion of mine is cleared out, have a good day or night guys.

I guess you missed the text after the game, or didn't click the link there.
It wasn't the OP, who was accusing others, it was their opponent. The opponent behaved terribly after the game.

@WildTiger Yes thats why I said in my first reply ''Even if you do get to a point where you suspect an opponent of cheating or if they are accusing you , REPORT THEM. ''