>Do any other Christian anons find this forgiveness difficult
I have not much ever struggled with unforgiveness. Any time I recognize or verbalize this inborn characteristic (because I take no more credit for it than should someone born with a beautiful singing voice) I think/say, "Lord, I'm not asking for any new tests against this claim." Kek.
I also take a Spock-like approach—I want to be forgiven and know my forgiving others is part of the deal. I can mostly emotionally divorce myself from the feelings and see that as logical.
Furthermore, I believe you can be truly forgiving and simultaneously celebrate their lawful execution. I would not be vengefully celebrating their personal demise, but celebrating justice being meted out.