I often read and heard about burning tokens that were not sold when the ICO project was finished, I also knew that by burning the rest of the token was a strategy so the price of the token didn't fall, but if the DEV and the team didn't burn it was a crime? is there a requirement that the remaining unsold tokens must be burned?
As a rule, this condition is prescribed in White Paper.
Judge for yourself - if the tokens remain, and the team just left them for themselves, how can you believe such a project? Likewise, they can take everything for themselves and close the project.