The Lannister dwarf is extremely, extremely lucky in one particular area. Tyrion was able to get away with king-slapping Joffrey straight around the face without feeling executioner Ilyn Payne's blade swiftly following through his neck. Tyrion is the people's (at home) champion, carrying out acts that we could only dream of. Joffrey needed a slap, and boy did he get one. Unfortunately for Tyrion, he would've had to get his slap-rage out in a certain window of time before it closed forever. He couldn't thwack Joffrey as a child, and he wouldn't have been able to reach a tall, matured Joff. The Boy King only had a few good slap-appropriate years, and Tyrion took advantage before the Gods kindly removed Joff from the face of the planet.