It is unethical to take away both the bonus balance and the original balance if a user has not completed it.
I do not understand why you would do such a thing. Additionally, the message you had in the bonus cancellation screen (and what you have said) was that you only cancel the profit.
Hence, if you are falsely advertising the amount that is deducted from a player's balance, then that is straight-up scamming them.
I have already talked about forcing a player to complete the bonus, so you can read my reply from above:
Here's the scenario.
You deposit a significant sum of money into the site with a bonus. The terms seem clear and they even state that you can cancel the bonus at any time. Hence you would expect it to deduct any winnings from the bonus (and for losses, it would not refund you)
You should not, under any circumstances, force the gambler to bet through the entire 55x wager requirement. For this site, you ARE forced because otherwise you will lose your balance. That is unacceptable conduct.
By not highlighting the risk of the bonus beforehand, you are essentially stealing their money: 55x is no small feat, considering you essentially need to bet your full deposit + bonus 110 times as per their rules. Even with a 98% win chance, that's a 10.83% success rate of getting through the requirement.
If you only cancel the profit, people can just keep playing with the bonus. Site would be bankrupt in a day.
If that was so I would deposit 1btc, take the reload bonus so I have 1.5 btc. Make 5 bets of 0.1 on 100x. If I don't hit, I withdraw and deposit again and start over. Best way is just to remove the cancel button. People just don't read.
The problem here is not Duckdice but just an user that don't read well.