Spoofing certs is not comparable to breaking RSA. Also, I think for this thought experiment, you should also consider breaking elliptic curve crypto. Neither has been proven hard.
Spoofing certificates was the example given in the parent comment. We use elliptic curves specifically because they are harder, in a specific way (resistance to index calculus) than simple multiplicative group cryptography.
My point is just that nobody is going to kill you for this ability.
