Example sentences:

Ramayana: Indrajita alleged that Vibhishana’s opposition to Ravana was tantamount to betrayal of Ravana. 

 Mahabharata: Duryodhana’s brazen attempt to arrest Krishna who had come as a peace envoy was tantamount to an act of war against the Pandavas.  

 Bhagavad-gita: Temptations are tantamount to attacks on our consciousness by the forces of illusion.