A sin that weakens our relationship with god is?

Protestant Answer

There is no sin that does not separate us from God. He is holy. When we sin, we are being unholy. The punishment for sin is death. But Jesus, God's son, died on the cross. He payed the penalty of our sins, so that we might have an eternal relationship with him. (John 3:16) "For God so loved the world that he sent his only SON that whoever BELIEVES in HIM will not perish but have EVERLASTING life.

This is all in The Bible. It is proven to be accurate by prophecy.

Catholic Answer

Venial sin - lesser sins