Use 'traitorous' to express strong negative feelings about someone's disloyalty. After the coup, the general's traitorous allegiance shocked the nation.
Pro Tip 2/3
Not Just Betrayal
'Traitorous' implies a betrayal of trust in a serious context, such as politics or relationships. He felt her selling the family heirloom was a traitorous breach of trust.
Pro Tip 3/3
Context Specific
The term often relates to betrayal in a high-stakes situation, not minor disloyalties. The spy's traitorous disclosure of secrets could endanger many lives.