Timing is everything: fire it late, once opponents have spent their Attacks or run their hands thin, and the free damage lands across the table. You're immune — only others answer — so it shines for a Lord boxed in by Rebels, or a Rebel pack closing out a low-HP Lord. One shot can clip up to seven. Never throw it while hands are fat, or you waste the trick.
Pair it with Hail of Arrows for a brutal double squeeze — one demands an Attack, the other a Defense, stripping every hand bare before you move in for a low-HP kill. Guan Yu and Zhao Yun fire it fearlessly: when someone throws a Barbarian back, they flip a red card or a Defense into an Attack and always answer, so they almost never bleed for free.
The cleanest answer is Negate — it cancels the entire effect and saves the whole table at once, so a Loyalist should hold one to shield the Lord. No Negate? Then never empty your Attacks; keep one in reserve, especially at low HP. Remember Peach and Eight Trigrams do nothing here — only an actual Attack card satisfies the demand.