I only can tell someone is cheating when he is spinning or use trigger bot which I can easily see because ppl with trigger usually have bad af movement but somehow they are hittin amazing shots and for confirm I watch demos after match.
I Have about 3,4 pages on my profile ppl writing "-rep cheating..." but I dont.
Probably OP could be one of them. If you dont check demo u cant say if he is cheating.
BUT I had situation when someone watched the demo and write on my profile about it and said Im cheating. Well I have good aim and it can looks weird on 32 tickrate demo. But he probably didnt paid attention to my movement and gamesense so his assessment of the situation wasnt that good