[bakugo]

If your goal is to just burn as much money as possible, as fast as possible, simply spamming expensive image/video generation requests would probably do the trick, if the key's rate limits are high enough.

There's also a practice that primarily seems to occur in china where stolen keys are resold via proxy services. A single key can provide access to thousands of users, racking up costs very fast (again, assuming the rate limits are high enough).