The most thing that makes me crazy about online is delay in withdrawal and kyc requirements, ie failure to verify kyc details when submitted to them and lastly delay delivery of deposit. What I don't really like is after winning and they published your winnings like not secure while dealing online so everyone casino should limit how to publish people's winning.
Apart from the delay in withdrawal there is another type of delay that drives me crazy. When you chat an one representative on an issue that could be resolved immediately from admin, but they will tell you to wait for 48 to 72hrs. For goodness sake it is annoying, just check your admin and solve this problem without making me to wait for another 3days.
Waiting for that long will really drive us crazy where in fact, they dont give us problems when depositing but when we withdraw funds, seems like they intend to create some problems because they didnt want us to withdraw our funds. If they cant solve a simple problem like that, then most likely they will not be reliable enough when certain high rollers end up winning such a huge amount. That will be a very big mess then.