A lot of people go on about the parallels between Marco and Toffee, but don't mention the parallels between Star and Ludo as much.
Star is the main protagonist, and Ludo is the main antagonist. He's the ice king to Star's Finn.
Star is a princess, and while Ludo is never referred to as royalty, he grew up in a castle and had a squad of goons to wait on him hand and foot, so he's probably more privileged (and I mean that in the actual way not the tumblr way) than the average monster.
They can both act foolishly, but have/had someone smarter as a sidekick. Star has Marco, Ludo had Buff Frog and Toffee.
In the season 2 premiere, they both learn how to adapt without something they had previously depended on or used as a crutch. Star learned to cast magic without her wand (which will probably be useful if Ludo/Toffee/someone else swipes it to cleave the wand together and/or set up the season finale) and Ludo learned to take care of himself and bend others to his will without the aide of his goons or the resources his castle had (I'm assuming the monsters stuck around because Ludo fed/paid them.)