Destroy means to damage something so badly that it cannot be used anymore or it no longer exists. Ruin means to damage something, but it still exists. Spoil means to damage something, but it still exists. It’s less strong than ruin.
destroy The building was completely destroyed by the earthquake. Many factories are destroying the environment. His car was destroyed in the accident.
ruin The rain is going to ruin my new shoes. Please, don’t ruin my hair with that cheap dye. Her career was ruined when she was fired.
spoil The lake has been spoiled by litter. Food will spoil with this high temperature. Don’t let this incident spoil your holidays