Luffy's resolve. Once Luffy decides something he's firm on it, no pussyfooting. This is what made him such a dope MC. Favourite example of this: When he decided Nami was his navigator. He doesn't live in the past, he refused to listen to Nami's backstory, he just saw Nami in pain and that was enough. He knew he had to kick Arlong's ass, the details never mattered to him.
Zoro's level headedness and loyalty. Zoro is someone who is just as dangerous if not more than Luffy at times, yet not a bone in his body hesitates to stand in line behind Luffy, and he understands his Captain's intentions immediately without even words being said.
Favourite example of this: Zoro could fold Bellamy and his crew by himself (and he was about to), yet he noticed Luffy not fighting back so he didn't make a move, then at Luffy's whim he took a beating without questions and hesitation, and was completely unbothered by it.
Sanji's charm and passion. What was lovable about Sanji is he can go from a straight bully/thug (the biggest dick in the strawhats easily) to this child with a glimmer in his eyes when discussing his dream. He can be the most cold-hearted person when someone doesn't align with him and then turn around and be the most compassionate person when he wants to be, this range is what makes him charming. Favourite example of this is when he was beating the brakes off a customer for being disrespectful, but then turned around and fed infamous pirates when no one else was going to.
I want to list out a couple more strawhats but I got tired of typing.