gloat

To feel or express great, often malicious, pleasure or self-satisfaction: Don't gloat over your rival's misfortune.
e.g.
The coach told his team, "There's only one thing worse than a score lose, and that's a mean winner. Don't gloat."
Neil's sister always tattles on him and then gloats when he's punished, saying "I told you so."
tattle: To reveal the plans or activities of another; gossip.