The Latte That Broke The Camel's Back

So here's my confession. I work as a barista at this cozy little café downtown, and to be honest, I'm not the most patient person in the world. But today was one of those days where everything went wrong. The coffee machine kept breaking down, people kept ordering the same thing over and over again, like they couldn't make up their minds or something, and then there's this guy who comes in every single day at 3 PM sharp for his triple shot latte with a twist that only I know how to do correctly. Now, normally I don't mind doing it; he's usually pretty polite about things. But today? Today was different. He walked in, ordered the same drink as usual, and then proceeded to criticize every single aspect of it. The foam wasn't frothy enough, the coffee-to-milk ratio was all wrong (even though I triple-check that now), and on top of it all, he had the nerve to complain about how long it took me to make his drink. I tried to stay calm, really, I did. But when he said those final words, 'This is the worst coffee I've ever tasted,' something snapped inside me. And so I decided enough was enough; this guy was going to get a taste of my frustration mixed into that latte. Instead of adding the usual amount of syrup and extra shots for his special drink, I added only half a packet of sugar and one shot instead of three. Just enough to make it taste like an average cup of coffee rather than the custom creation he expected. And then? Then I handed him his drink with a smile. 'Enjoy your coffee,' was all I said before walking away. The rest of my shift went by in a blur, and now here we are. I've come to this confession platform for two reasons really: 1) To see if anyone else has ever done something like this and how they handled it. 2) And more importantly, to hear what you guys think about what I did. Was I the asshole? Am I justified in taking revenge on a customer who's been rude countless times before? Let me know your thoughts!