Evan's charged Slenderman with intent to kill twice, but admittedly his much more badass attempt was in Ashen Waste, when he charged Slendy with a baseball bat. He fails, but he immediately asks "Did I kill it?" when Vince and Jeff are helping him up. Upon being told he didn't kill it, he says that he "should've brought my knife" before coughing blood all over the pavement.
Now probably topped by somehow beating the Rake into unconsciousness and throwing it out a second story window.
In a later fight he somehow managed to tear off its head, but that sort of backfired because then he had to deal with both the Rake's decapitated head AND body attacking him at the same time.
In addition to being a Crowning Moment of Heartwarming, Evan helping Alex and Jeff deal with the Rake in "Alex" is pretty badass. He's the one walking around with a huge knife and a flashlight who sticks his head into the closet where the hellbeast has been coming from.
And, unlike that poor exterminator, came back alive.
Jeff gets one of these in "Damsel" when he dive tackles a security guard much larger than himself
And now, all the above have been topped by the recent long awaited reappearance of a now Leather Jacketed, Cigar Smoking, Cheesy one Liner(ing) Dr Corenthal whom not only rescues Vinny from the Slenderman, but almost instantly becomes one of the (if not THE) most badass characters in the entire Mythos when he both calmly shoots Slenderman with a revolver but more importantly (and unlike Evan, Jay and Zeke whose attempts failed badly) he actually succeeded in driving him away with zero negative effect on himself or on Vinnie. Bad. Ass.
In a crossover moment, Firebrand implies that HABIT assisted him in breaking free of the Administrator's influence, meaning that HABIT managed to break someone loose from Slendy's sway.