To call Lt Joe Tormolen the dumbest redshirt kind of downplays just how dumb he was. He was a blueshirt, so he signed up as a scientist on a space mission when he didn't actually believe that people had any business doing science in space. Then despite being a scientist in full protective gear investigating mysterious deaths, he thought it'd be fine to take his glove off, start touching stuff, then put his hand under his hood to smell it. Spock came up afterwards and told him not to touch anything, but he decided not to report what he did. End result: his entire crew nearly died.
The dude was literally too dumb to live, as even McCoy and all his technology couldn't save him from a minor knife wound to the gut. Meanwhile, the rest of the crew were dealing with a condition that impaired their decision making and were still able to escape the planet, cure the virus and invent time travel. Because of what they learned dealing with Tormolen's stupidity, they were able to save humanity from the Whale Probe and restore whales from extinction. This also meant that the Enterprise-D crew had the information to make their own cure and save themselves from an exploding star, and Picard later used slingshot time travel to save the Federation from becoming the Confederation.
Basically, Tormolen's stupidity is the linchpin of the Prime Timeline. But Olsen was the stupidest redshirt in any reality.