Not true — if the dose is high enough, you could gain the power of enhanced dying.

Turbo cancer.

Reverse healing.

There's a reason only Silver Age characters have that as their origin: Fantastic Four, Spider-Man, Hulk. Back then they didn't know yet that radiation causes cancer (and once that was proven, they used it as the way Captain Marvel died — he got blasted by something and developed cancer from it, and since his powers made him immune to poison, chemotherapy didn't work and he died). Miles Morales' origin is a genetically modified spider, not a radioactive one.

To be fair, Spiders-Man wasn't just one bite. Peter fell into a vat holding a huge colony of radioactive spiders and they ate him or something.

I hate when that happens.