Helm from the novels of course, not those moronic movies.
Trav can be an ingenious, sneaky bastard, but I figure Helm could take him easily enough. Snipe him at 300 yds on the deck of the Busted Flush, knife him at close range during a crowded party on the Maynard Keyes or maybe put something from his syringes into the Boodles.
I have to plead ignorance on Helm and his abilities. And I’ll concede that Travis or anyone else is vulnerable to a totally unexpected, bolt-from-the-blue assassin.
But Travis’ survival skills should not be underestimated. He’s careful, sneaky and lethal. Give him some hint that he’s in danger and he can turn the tables damn fast.
How 'bout this? Plop them both down in the middle of a Florida cypress swamp, tell them there’s someone else out there trying to kill them and give them each a pistol. I wouldn’t bet against McGee in a scenario like that.
Helm would whack McGoo immediantely.
He was in a plane with the bad guy and the pilot died.
Helm: “Can you fly the plane?”
Bad guy:“Yes”
Helm BOOM!
Lest the bad guy survive.
Indeed, one of the Donald Hamilton novels climaxes in a Swedish marsh where Helm pretends to be unable to navigate and when the villian is out of sight for several hours begins the famous woodland stalk of his foe.
When he was recruited, Mac asked Helm if he was a hunter and if he had a problem hunting Nazis.
Helm responded, “You mean stalk them in their native habitat, Sir?”

You know, I was just about to give you the win. If Helm is that much of a psycho, then our rational, knight-in-rusty-armor Travis would hesitate and get his head blown off, I thought.
Then I remembered just how many psychos have died while trying to kill Travis McGee and I realized Helm would just do himself in somehow.
Trav would show up just after Helm had killed his brand-new love. While Trav is cradling her body and remembering the gentle whisper of her breath as they made love aboard the Busted Flush, Helm would attack from behind. Then they’d beat the crap out of each other, rolling around in the swamp muck.
Travis would win the fight and tie Helm up so he could take him back to the county sheriff and prove that old Harris Bigfortune didn’t commit suicide over the failed land deal, which means his young bride should have inherited his insurance settlement after all (if she hadn’t just been murdered, I mean).
But as Travis is remembering Meyer’s wise, wry commentary on the dangers of love, Helm would wriggle out of the ropes and run for the gun he had dropped in the struggle. With the soulless look of a true sociopath (the kind of look that Sgt. McGee remembered well from that hot, damp jungle war when he _ what? Oh yeah, the fight … ) Helm would pull the trigger. But he wouldn’t realize the barrel was jammed with mud. It would explode in his face, killing him instantly.
Trav would then bury Helm in the hole where the rest of the Bigfortune money is hidden, then go drown his sorrows in the warm, willing flesh of all the swingin’ girls partying with the Alabama Tiger.
Sorry, but that’s what happens to cold-blooded psychos who go up against Travis McGee. It’s some kind of pulp-fiction law of physics.
McGee, and it ain’t even close. Helm sneaks aboard the Flush in the dead of night, but Travis feels the boat shift slightly.
Travis sneaks up behind the sneaking Helm and gets him through the throat with a marlin gaff. Using the gaff like a handle, Trav drags Helm’s body out to Miss Agnes, throws it in the back and drives out into the glades about 30 miles west of Lauderdale.
He throws what used to be Helms into a 'gator hole and returns to the Flush to find the warm, cuddly brunette already stripped and snuggled into his bed.
Ho, hum; just another night at Slip 18.
As I recall, McGee has a lot of quick. (And favors an extended elliptical rhythm when pleasin’ the ladies.)
This thread makes me want to read the Matt Helm novels now. Sounds like the (admittedly moronic) Dean Martin movies were Matt Helm in name only.
Just for the record, Helm isn’t a psycho, he’s a government employee. 
Got to go with McGee also. Not because he’s smarter, or stronger, or craftier, or more skillful, or more ruthless…since he’s none of those things. Nope, as we have seen in a bazillion novels, McGee has shit-ass luck on his side and there is no substitute for that.
And even if he is drunk Travis just rolls out of bed and sweats it out on the road. Give it to the rainbow man, although he won’t kill Helm…he will end up as Trav’s boat boy.
Are you insinuating that McGee plays for the other team? 
The first is Death of a Citizen, the second The Removers.
Here is a scene from the second; Helm has let the bad guy beat the shot out of him for four hours.
I covered up and backed away, hearing Martell laughing heartily behind me. I heard his laughter stop, but He’s made his mistake. He’d forgotten I was supposed to be dangerous. I’d worked hard for that forgetting, I’d paid high for it, but it was worth the price. When he realized his error, it was too late, I was too close. I was right there.
I dumped the table on top of Joey. The big Jaguar tire helped. Sliding off, it took him right in the chest. I turned, and my timing was perfect. The gun was just coming out from under Martell’s coat. I gave it to him with the stiffened fingers that’s worse than the blow of a fist. He double up, paralyzed, and I had the gun.
I shot him with it once and threw myself down, and Joey’s first shot went over me. It was all he was entitled to. It was close range and I could aim for the head. The first bullet just punched a neat round hole, but the second kind of blew things apart a little. Scratch Joey, who had one good impulse in his life if it was that. Well, many of them don’t even have one.
(Logan the Brit points out that Martell is still wriggling)
“You’d better attend to our friend over there. I believe he is reaching for another weapon, At least he is still alive.”
“I can’t see any necessity for that”, I said and I went over and shot Martell through the back of the head.
Shit.
Beat the shit out of him for four hours.
Dammit
Thanks, carnivorousplant. Okay, now I’m definitely checking out those books.
Enjoy! BTW, The Removers is #3.