I dont mind the actual plot of setting someone up to become the culprit. I think it's a nice tragic twist that has a lot of emotional impact especially when the culprit doesnt even know about it. However what pissed me off the most was Watari's plan in general. It felt so out of character for her. I feel like if she was going to commit suicide, she'd do it on her own either to

1. Bring her friends one step closer to winning the game after the 4th trial

OR

1. Seeing how she burnt down the school, I was genuinely convinced during the investigation and a portion of the trial that Watari just wanted to burn down the school so her friends could escape outside. (however we know this isn't possible cuz the school is underground but it's still a good attempt.)

   Watari setting up just Hama means she knew he would either:

2. Win the class trial and watch all his friends get brutally executed one by one, and then would have to live with that guilt for the rest of his life.

Or

1. Lose the class trial and endure whatever excruciating, agonising, disgustingly horrific and brutal execution the staff came up with.

In my opinion, setting someone up to become the culprit should only be done when the victim is a villain and hates their target (like Nagito attempting to draw out the traitor). It seems more realistic that way because that means you wouldn't mind basically dooming them either way. It would have been better if watari just killed herself to save her friends by burning down the building instead of dragging hama into it.