10 Times Batman Went Too Far
4. Evaporated Ra's Al Ghul - Batman Annual #8
The crux of Batman's entire dynamic with Ra's al Ghul is that Ra's wants him to take over the League Of Assassins, which of course means Batman has to kill him. It's a great dynamic because we know Batman will never do it even though Ra's gives him every reason to WANT to, and getting rid of him means that he can be with Ra's' daughter Talia without her father's machinations getting in the way.
Which is probably why Batman just straight up chose to vaporize him at one point.
In Batman Annual #8, Ra's has introduced a chemical that, when consumed and paired with the red sunlight emitted by a space station that Ra's somehow has, immediately kills them by way of evaporation. Definitely one of the more painless and merciful of Ra's' murder plans, but a murder plan it remains, so Batman, Robin and Talia chase him down.
After yet another duel between the two formidable warriors, during which Ra's had them both drink the chemical so that the loser would be exposed to the red sun radiation, Ra's tries to get away on a spacecraft. However, Batman shines the red sun energy on the space craft, dissipating the guy right in front of his daughter.
I know rules are rules and all, but this is probably why Talia didn't feel the need to tell you about Damian until she HAD to, dude. Just saying.