Is this a red flag or am I overthinking??

[Cherylyn]

He's huge red flags all over the place and he's very mentally sick.  ☹️  He gravitates towards violence,  gory scenes,  cruelty and gets angry easily.  He's one sick dude.  You need to dump him.  Make him your ex-boyfriend.

[jul-els]

Neither one of you is right or wrong for feeling the way you do about it. The question is does he respect your feelings? I’m this case no, he didn’t. That’s something worth talking about with him and something you should decide if you’re okay with. 
 

Edit: I just read the rest of the thread. You already know the two of you are not compatible. It’s time to move on with your life and find someone who’s more aligned with your values and philosophies.

[ShySoul]

23 hours ago, blue_night said:

Another example, he has once witnessed someone jumping from a bridge to his death a few years back. When I asked him "how did that make you feel?" He told me "I felt nothing, just kept walking"

Here is your red flag. As much as I love animals and don't want to see them hurt, this was a human being. He saw a person die in front of him and felt nothing? If he has that little regard for the well being of others, how could you ever expect him to care about what happens to you? It doesn't even have to be him doing anything to you. What if you had serious health problems and ended up in a hospital? Would he shrug it off and say "I feel nothing?"

20 hours ago, blue_night said:

I feel like there are more reasons to end it than reasons to stay. How should I go about this and cause him the least pain in the process?

Honesty is the best policy. Tell him his anger and lack of empathy is not something you are comfortable with. You wish him well, but you don't think this is the right match for either of you. Stand your ground and don't let him try to convince you otherwise or get angry and turn it around on you. 

As for causing him pain, theres a good chance he won't feel it. He seems to not feel so much, at least when the pain is happeneing to others. Hmm... maybe him feeling a little pain might actually do him some good.