I will not mention any particular gambling casinos, but what are your thought if the casino or casinos with good feedback from the community, but with one unresolved scam accusation but from all angles, the accusation is legit with all the screenshots, transaction hash email conversation are provided by the complainant lets say he is not allowed to withdraw his earnings amounting to $100k but from all angles the accusation is valid, don't you think with thousand good feedback, its enough for the casino to lose his reputation with one legit accusation.
If a big casino is ever going to scam a player, the amount of coins, that are stolen would probably be big.
I don't think that the big casinos would destroy their reputation by scamming multiple players with small or medium amounts of coins/money.
So to answer your question. No, I don't think that a big and valid scam accusation could completely ruin the reputation of a casino, which has thousands of positive reviews. The reasons are two:
1.Many people won't be aware of this particular scam accusation.
2.Many gamblers are betting small amounts and they know that the casino won't scam them for peanuts.
One, legit accusation has the possibility to break the casino's reputation if the person who claims to be scammed will file a case to the authorities. If that person is powerful enough, one post and share to social media could gain many engagements and side comments which could affect the casino's credibility most especially if the evidences are also posted. There are many avenues to direct the allegations with proofs not only in this forum if the accused is not cooperating well. However, of course there is still a proper venue to address the problem.
On the other hand, it can also be neglected and overlooked because some people might think it is just an isolated case given that there are many positive reviews, but only a few bad reviews. If collective bad reviews and comments were to be collected, there's a higher possibility that people will not trust the casino anymore. Although certainly, some will still use it despite the bad review most especially if they haven't experience it and if it works well for them still.