Although Carl he felt extremely guilty for betraying his closest friend for doing this to him, however, Carl will never regret it, just like Z that has a dream, wish and hope, he finally found what he wanted in this life of his where in the past, he can only follow along without a dream of his own, watching how dazzling, bright and full of life Z that has a direction on his life.
"... Z… I am sorry… but to make Henry look for me… I need this power… besides, I believe that the family that you are targetting was the family that he belongs with…"
So in the end, Carl can only choose between his friend Z or the man he loves Henry, he was just glad that there were those fortunate circumstances that his drunk friend that has his guard lowered down has once murmur which family he was targetting the most.
Despicable of him, yes, but Carl just know what he wants and has chosen to betray his friend for it.
