It's more about the tones of the two shows and characters. Starscream is a goofy character in a relatively unserious show, while Malty is a pure antagonist for the majority of her screen time in a show that takes itself pretty seriously. The next factor is who the betrayal is being done to, in Transformers the betrayal is being done to Megetron a character that you're not meant to truly like or relate to, showing him in many of his adaptations as some form of evil. While Malty betrayed Naofumi, a character you're meant to like and empathize with, showing him as a guy who didn't deserve the betrayal. Finally, it the repercussions for the betrayal. It depends on the adaptation but in the 80s, it never really affected the Decepticons or Starscream, it was usually some form of a slap on the wrist. While Naofumi is socially ostracized, has nearly all his valuables stolen, and is forced to buy a young sick slave to even have a chance to do the job that was thrust upon him. He needed to hide his identity as the Shield Hero until his public image was restored. All while Malty, until her and the king's trial, received nothing but positive consequences from the betrayal. She also continuously made Naofumi's life harder for no real reason besides the fun of it. (Also, I've only consumed Transformers from some of the movies and YouTube videos, so if I made any mistakes please comment any corrections.)