I gotta say i partly disagree on this post. Yeah he is a bit too nice and naive, but he has a method to it. He isn't the blind/stupid hero type like kouki from arifureta, for example.
His main thing is that he sees the good in people. Not so much just blindly assuming the good is there, but actually seeing the good that is actually there. He's been through enough that he doesn't blindly just beleive all people are good, but he sees the good in them even when they don't see it in themselves. True it took him a few disasters to get to that point though. He would never have helped lili, haruheme or the xenos otherwise,
That's why he wants to save freya despite everything she did to him. Yeah she deserves to be punished, but at the same time he saw something in her worth saving.
And when he stopped lyu killing jura it was to save her, not him. Saving people also means saving their souls too. She had stopped her killing spree 5 years before and he didn't want her consumed by revenge again.
He has also had times when he showed no mercy. Fighting Apollo familia. He didn't hold back or try to save them. He crushed them. Fighting the berbera. He went all out and didn't hesitate. Fighting dix and ikalos familia. He absolutely didn't hold back. I'd say dix is the one person he truly grew to hate since coming to orario. Though even without holding back he doesn't resort to killing.
As for the girls who fall for him. There are those who fell for him because he saved them, body and soul. Ie lili, haruheme and lyu. That's also why bell fell for ais. That is a reasonable scenario in these kinds of stories. The problem is with the others who fell for him just because he is kind. Like hestia, eina and cassandra. Too often, both in stories and in real life, being kind to someone is interpreted as them being interested, or having feelings for them. When really they're just being kind. That's how the whole friendzone thing happens. Yeah that can also happen for a character like bell, but too many just gets ridiculous.
So anyway, yeah he is a bit too nice and forgiving at times but he isn't blind to peoples true nature. If he sees something worth saving then they are worth saving. If he sees nothing good in someone, especially an opponent, he doesn't hold back in stopping them