Trump has admitted that Jr's motive in attending the meeting was getting dirt and also claims he himself is not aware of the meeting. Jr testified that he never told anything about the meeting to Dad.
Even if Dad does not know about it, Jr is guilty of conspiracy as Trump has admitted to the purpose of meeting.
If Dad knew about it, Jr is guilty of lying in testimony in addition.
But, if Sr is saved and only Junior gets locked up, then it is easy to fix using a pardon. If it is the other way, then it cannot be fixed.