"Acquire friends. Acquire power. Acquire happiness. Try to publicly join a faction, if any will have you, so that you aren't a loner associated with the one Death Eater that even other Death Eaters repudiate, but are instead associated with respectable Slytherins. If Slytherins won't have you because you're worthless as an ally, try moving to Hufflepuff. Note that Neville was willing to defend you from bullies; make him and others like him like you. Publicly repudiate your mother if plausible."

I like this idea, except I'd leave out the last bit if it were me. You've already left yourself some wiggle room with the "if plausible," so you probably wouldn't get Lesath into much trouble that way, but given what we've seen of him fanatic & public loyalty seems to be a big part of his nature. It's probably the only reason he's in Slytherin (loyalty to the idea of Slytherin, I mean--I bet he had to beg the Sorting Hat, as otherwise he seems completely unsuited to the House). It looks like he's formed his identity around that loyalty, and it might do a number on his head if he had to suddenly act in an inconsistent manner.

That capacity for loyalty would make him a great minion though. Harry already caught himself wishing for a Bella of his own, and now! Here's her son, pledging his life...