She’s easily the most powerful one besides prismo, possibly finn, possibly bubblegum, possibly ice king, and jake, Hunson, Golb, and the lich

not so much, only when he came back from death

How?

at the beginning of the Estacas arc, Marceline in her words to jellybean said that bad things happened to her when she was a child, and in fact, she lost her mother, she was one of the few survivors of the mushroom war, Simon had to leave her with Hunson because of the crown driving him crazy, even if he sent her letters before he went completely crazy, it wasn't the same thing, and Hunson was horrible, when she was a teenager she became a vampire, and again in Marceline's words at the beginning of the Stakes arc, when she became a vampire she was very disturbed, and 1,000 years passed and she still felt disturbed, and she wanted to grow up, she thought she was her mistakes and what she went through, but after defeating all the vampires again and go back to being a vampire but this time with very fresh mortal memories, and maybe more affection, she felt more mature, realizing that she had really changed, and she was okay being a vampire again, according to her being mortal was cool but it was also sinister, and right after she realized these things she sang "Everything Stays", which is a very touching and deep song, and also seems to make a reference to Marceline's own story, and no, the song "Everything Stays" is not a Foreshadowing of the Spinel story from Steven Universe, Rebecca who wrote the song, but the song was based on something that happened to Rebecca that inspired her to create this song, and now she has someone who she knows she can always trust, Bonnie, also known as Princess Bubblegum, and the relationship they built in the series is clearly deep in Obsidian, because from the looks of it, their story has already been planned since we saw the two interacting in the series for the first time, and in Obsidian we discovered why the two were always teasing each other, and the way they managed to rekindle the relationship was very well constructed

Shwabie. When she first became a vampire she ate the red off her poodle nearly killing the dog after she ate some blood too. Then she used the enchiridion to turn her dog into a half ghost .

Have you watched the Stakes Arc? It's where Marceline becomes normal again by her powers taken away, but that power morphed back into powerful vampire lords she killed so long ago. At 5:04 is one of them and she absorbed his powers of shape-shifting

@@bjuganda7758 well it's been awhile since I've watched the entirety of the show.

Before she became a vampire, she was a vampire hunter, and one of her opponents was the Hierophant, a member of the Vampire King's court who had shape shifting powers. When she killed him, she sucked his soul with her demon ability which granted her his shape shifting ability

@@Mauricio0973 ah, now I remember.