To quote a previous poster:
"I want to say Scotty, but I keep remembering his insistence that it takes 30 minutes to restart the warp drive in "The Naked Now" ("I can't change the laws of physics.... I've got to have 30 minutes!") vs. Trip doing the same thing in "Divergence" in 2 minutes ("That's impossible!", "Watch me!")"
I couldnt agree more. Trip was the engineer of the first warp 5 ship. he wrote the book. Scotty( in all his brilliance) just read it .
Scotty had the benefit of having almost 100 years of humans experience with flying god knows where around the Alpha Quardant, while tinkering with Warp 5,6,7,8,and 9 ships before him. Not to mention whatever knowledge the Vulcans ,Andorians , and Tellerittes gave to the Humans as part of the mutual contributions after the Federation was created.
Tpol called what Trip did "impossible:" Even though she wasnt an engineer its still Very high praise coming from her.This is from a Vulcan who part of a species that possessed warp drive centuries before humans did and all without anyones help( except for that engineer from the episode Cogenitor.)
Still Scotty kept himself alive for 75 by rigging a transporter.... Something Laforge called "a genius"
Honestly want to give it a a close tie between Trip+ Scotty,but if had to choose as much as i bow to Scottys brilliance, Trip gets extra points for being older and not being a starfleet grad, and not having anyone come before him like Scotty did.
Scott did say it takes 30 min to restart a warp drive.. Trip outdid him there.
Plus Scott lives alot longer, in fact as far as the canon goes, hes still alive BY the end of the TNG timeline in Nemesis.Trip did all that and he was in his mid 30s before he died young.
the only thing that puts Scotty almong the best was his transporter lifeboat idea, but for all we know Trip might have come up with the same idea( to survive in a pattern buffer)
I certainly wouldnt put it past Trip. Trip had NO ONE come before him and he still made his miracles.
I bet if Trip had made it to Scottys age ,i have no doubt Trip would be twice the engineer Scotty was.