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.
This is what can make anyone to be crazy about online casinos, their is nothing else that can make someone to be mad if not delay of payment, finding it difficult to complete process to withdraw.
If casinos can make withdrawing process so fast , I don't think people will have any hard feelings concerning online casinos.