WARNING: The following contains spoilers from Star Wars: Darth Vader #17, on sale now from Marvel Comics.
When Senator Palpatine began tempting Anakin Skywalker with the Dark Side, it was clear that Darth Sidious was more interested in his raw power than his brain. Palpatine knew that Anakin could tip the scales of balance with the Force and help turn his Republic into an unforgiving Empire as Darth Vader. But as Star Wars: Darth Vader #17, by Greg Pak, Raffaele Ienco, Alex Sinclair and VC’s Joe Caramagna, Vader could still make stupid mistakes, even if he was a powerhouse and a force to be reckoned with.
That detail has become perfectly clear as this comic explored how he wanted to find ways to usurp Palpatine, and it culminated in Palpatine breaking him down on Mustafar, abusing and putting Vader through new trials so as to burn out the Jedi remnants in him and make him a more sadistic apprentice, burning out the last apparent traces of his love for Padme.
This has led to Vader partnering with Ochi of Bestoon, as Vader wants to find Han Solo's frozen body so he could lure Luke Skywalker in for a trap. However, as he baits his son, it's evident Vader should just go back to Coruscant and murder Palpatine. By this point, Vader seems to know that Luke will never join him, and he knows that Palpatine merely wants to replace him with Luke. It gets even worse as Sly Moore, the Umbaran working with the Emperor, sabotages Vader's plot to grab Solo and kill Luke, making it clear Palpatine wants, and more so, needs the boy.
She says as much in front Ochi, Vader and Mas Amedda, right before Vader's mission failed. He ended up killing Bokku and the Hutts out of frustration, so he clearly knows things aren't going his way. And as Sly speaks, the root cause of all this is Palpatine's search for a new apprentice. However, Vader chokes her instead, deflecting his rage at the wrong person.
As the Emperor phones in, Palpatine taunts Vader, blatantly misdirecting him to hunt Crimson Dawn down. He flaunts his ego and narcissism, challenging Vader as he doesn't want him going after Luke and endangering his prize. At this point, it doesn't take a brilliant strategist to see he's eyeing Luke as Vader's replacement and poking fun at how oblivious his war dog is to the obvious truth.
This makes Vader look amateur, hearkining back to his blank-minded, rash days that left Yoda, Mace Windu and Obi-Wan Kenobi wanting him to be more sound of mind and judgment. Sadly, all the red flags and warning signs are there Palpatine will pit Luke against him. But rather than trying to kill Palpatine himself, Vader pursues the tougher, more emotional quest that'll expose him.