"If we fail to forgive, we are in danger of not being forgiven."
If we fail to ask God for forgiveness before we die, we are in danger of permanent separation from God in the next life.
God will judge, and there is no doubt he will judge murderers more harshly than traffic-violators.
Which person of the Godhead is going to judge you to send the believer to hell?
But you don't have any support for one sin being greater than another. In fact, liers are lumped in with murderers in several passages.
How do you determine what is or is not a greater sin?
All sin is sin.