That happens, you won't be the first LOL.
Two ways to undo it; use the starter motor trick (and a stronger breaker bar
) - wedge the breaker bar on the chassis leg by battery (wrapped in a rag to stop scratches/dents etc.) and click the starter motor for half a second. Usually works first try.
Or the more "correct" way is to take out the radiator and get an impact wrench on it.
Both methods to be done with caution (rounded bolt heads, knackered crank thread/woodruff, sheared bolt, another broken breaker bar etc.)