Revenge size is the sizing half of revenge-trading. The setup may even be legitimate; the size is not, because it was chosen from the amount lost rather than from the risk of the trade.
The arithmetic is unforgiving. Doubling size after a loss means one more loss puts you three normal units down. Two more puts you in territory that requires a rally to return from, which is exactly the situation break-even-effect uses to justify the next increase.
Size must come from a formula, not a feeling. Write it down, check it against the order before sending, and treat any deviation as a logged rule breach even when the trade wins.
Related: revenge-trading, break-even-effect, position-size-creep, size-up