I ruined someone's life. I feel no remorse.
Were you trying to ruin that person's life?
I feel no remorse from my past actions. I know that my actions ruined someone's life.
Even if you do not feel remorse, it is ok. Just try to logically understand how what you did could affect that person. I am sure that you would not want someone else to do that to you.
Feelings do not matter. I'll never change.
Feeling matter to some people. In addition to that, the more you ruin the lives of others the more issues you will have coming back to you. This will in turn ruin your own life.