You had to fight Solar, you didn't have a choice, you thought of it as a boss fight so you didn't think much of it since it had to get done. The fact that he was also trying to kill you wasn't letting you feel sympathy for him.

You did a lot of damage to him as you continued to land hits on him with your bat that was now soiled with blood/oil(?). It matched your own blood on you in some places from where he landed hits on you (very painful became he had machine strength and was made out of metal 😭), it hurt but to you, getting this over with was more important. You swung at him repeatedly and knocked him around with your bat in many different places... It look like it hurt, but no time for sympathy now, this guy was trying to kill you for Pete's sake! These were urgent matters, this was life or death over here! You mentally noted that he was getting slower with his attacks and morely focusing on his defenses as that's all he had the energy and mind left for. You hit him in the head harshly as he had failed to block your attack and he got knocked onto the ground, he looked damaged. He was all broken up and looked like he was on the brink of death again as his expression became more dull and his eyes started to loose their light, his faceplate was cracked badly and he was falling apart...

Solar: "M-moon..? Why are you waving at me..? I'm gonna die again, aren't I... I didn't even get a chance to say goodbye.."

His breathing grew ragged as he struggled to breath. Their were 'tears' welling in his eyes as he gave up and accepted the fact that he was going to be killed (again) by you this time and unfortunately probably not going to be given another chance at life this time, he thought of moon... Now you had the chance to end it all here, to finish him while he's down and done... Do you have the heart to..?