Sometimes the simplest of kills are the most effective, and the Punisher proves that sentiment to be true with his most R-rated attack, one he could use to take out Shang-Chi despite the Master of Kung Fu being far superior to the Punisher in terms of hand-to-hand combat.
Shang-Chi was trained from a young age to be unmatched in combat by his father, Zheng Zu, essentially making him one of the deadliest fighters on Earth. Since then, Shang-Chi has refined his skills so much that he has been able to lend a hand in training Spider-Man and has even taken on the likes of Thor in battle. The Punisher, on the other hand, knows some forms of martial arts but mostly just relies heavily on his weaponry. Frank Castle learned everything he knows about killing from his time as a Marine in the United States Military. When his family was gruesomely murdered, he applied his military training to vigilantism and became the nearly unstoppable killing machine fans know him as today.
While the Punisher has a high kill-count, there is still no way he’d be able to beat Shang-Chi without a gun as Shang-Chi cannot be matched hand-to-hand as shown in his many previous exploits. However, the Punisher proves that he’d be able to pull it off with a fighting technique of his own creation made specifically for taking out extremely deadly targets quickly and efficiently. In Punisher #2 by Garth Ennis and Steve Dillon, the Punisher is tracking a specific crime family and is systematically killing all of their known assassins. One of his targets is a master in all forms of martial arts, so the Punisher has to use his own creative technique against him, one known as Splat-Fu. The specifics behind Splat-Fu is the Punisher sneaks up behind anyone who could take him hand-to-hand while they are waiting for a train in the subway, and pushing them onto the tracks just as the train pulls up to the stop, resulting in the ‘splat’ hinted at in the name.
While the Punisher may not be as skilled as Shang-Chi in a close-up fight, he is a master at recon and, if his sights were set on Shang-Chi, he would be able to follow him into a subway station without the Master of Kung Fu noticing. After that, the Punisher could use his Splat-Fu technique without further incident, just as he did with the other martial arts master who he avoided actually fighting as a result of using this move.
Given the cold-natured brutality of just pushing someone onto subway train tracks and the fact that the act itself is played up as a joke, Splat-Fu is easily one of the Punisher's most R-rated attacks. However, some may argue that, while it is gruesome, it is also a cowardly move that shouldn’t dictate how the Punisher could take on any other Marvel character, Shang-Chi or otherwise. While that sentiment may have its merits, it is fundamentally incorrect all because of who is using the attack. The Punisher has no shame, guilt, or remorse and he will kill anyone he wants in any way that makes sense and ensures his victory. If the Punisher needed to kill Shang-Chi, who is very similar to the assassin he took out in this issue in terms of combat skills, then he could easily do so with Splat-Fu, and not think twice about it.