Any of the bachelorettes. Don't get me wrong here, I love their personalities, I just wouldn't marry them.
Emily: Love her, but a little bit too extroverted for me
Haley: I know her story arc is amazing, I just wouldn't marry her.
Abigail: She's my bff in game but seems... a little too young??
Maru: Feels definitely too young, and I like her more as a sister-in-law. Also, I definitely feel like I'm limiting her future by marrying her.
Leah: Also a great character, but I feel like I'm limiting her art career by marrying her.
Penny: Again, I love all of them, but I think Penny should explore the world a bit, and try new things!
And a few of the guys:
Sam: Great character, but too immature for me.
Shane: He's got a great story arc, but he seemed to relapse when I married him.
Harvey: Sweet dude, but a little too old for me.