tantamount to something having the same bad effect as something else (Oxford)
being almost the same or having the same effect as something, usually something bad (Cambridge)
If he resigned it would be tantamount to admitting that he was guilty. (Oxford)
Her refusal to answer was tantamount to an admission of guilt. (Cambridge)
tantamount to admit
tantamount to guilt
Alike
Equal
Different
Opposite
Tantamount