Great question - I absolutely have my ethics nailed down and I continue to compare them against my actions, and against reality, because one of the very first workings I did when I committed to the LHP was to run what 12-steppers call a “frank and fearless moral inventory.” Now, 12-step groups are not my thing, in fact I dislike them, but almost every school of thought has at least one valuable idea, and it pays to be open-minded enough to adopt any that have merit (dates for fertility, from the Qu’ran, being the last dietary change I made!).
When I ran that “inventory” I realised that a LOT of the stuff I was carrying around as guilt or shameful inadequacy was actually clutter or half-absorbed ethics from worldviews that made absolutely no sense, so in the spirit of the 12-step system, I made amends where possible and where this wouldn’t harm anyone, absolved myself of anything where that was appropriate, and moved on. I highly recommend this for anyone entering the LHP and looking for a ritual to break away from bowing to external morals.
With that work done, “evil,” to me, is anything that fundamentally and systematically seeks to limit choice, where that choice involves more life, more flourishing, more freedom to explore potential and live in a natural and healthy manner, and more enjoyment, for all sentient beings on a scale beginning with ME, then my immediate and extended family & folk, our pets, and down through various degrees of importance which includes farm animals, animals in the wild, even bugs and crawly critters.
Anything that sets itself up - I’m looking at you, Abrahamic religions, and also marxism and its manifestations - to nip that in the bud at an early age (in humans) by indoctrinating children with fear to prevent them thinking and exploring the spiritual realms for example - anything that does this en masse to animals, as with inhumane intensive farms, puppy farming, breeding pedigree dogs with genetic defects that mean they’re born sick, all that, to me, is equally evil.
While what’s “natural and flourishing” is a matter of some debate, what opposes and suppresses that is almost always recognisable, whether it’s the child-bride raped into PTSD (soul loss) under a patriarchal religion, the kid brought up thinking he’ll go to hell if he explores why he can see the future sometimes, or the cow that never sees daylight in her life because allowing her that small freedom would put 15% extra on the price of a carton of milk.
Unlike other definitions I’ve played with over the years, this one starts with me, right on the other side of the Divine Paradox, of being in that state of apotheosis, experiencing Self as the One sole source of all creation - anything that tries to limit that (mass religion, skeptical atheism, etc) is evil to me, on a continuum with stuff affecting (on the flipside of the Divine Paradox) every other living being.
That’s what I’m against.
And for my own conduct, in place of prohibiting ethics, I have values - positive things that I can aspire to, so my value of “I like animals” may equally extend to going out even though I have flu, to walk my dog - or, equally, sending an excrutiating death curse against someone who I know was cruel to their own dog.
Try parsing that under “LHP values” and it works just fine - try rationalising it under “RHP ethics” and you’re in a world of moral compromises and equivocations.
And such has always been the case, when people have tried to honour their values, whilst having to pay lip service to fixed external ethical guidelines.
I believe this is because we live in a universe of desire - of desire for more life, more love, more going-towards of all the things we treasure, and that the atrophied dead claws of RHP prohibition and externally-imposed restraint are, at their core, anti-life - as can be seen in their practices of hating women, hating sex, and forbidding exploration of any kind that may threaten their dogma.
They sing a good song about “love” and put a good spin on things as being “for the highest good of all” but there’s always an undertow of hypocrisy, because sooner or later the religions of love will kill their enemies, and the atheist, skeptics, and marxists who believe only this life is real or valid will remove that life from anyone who happens to challenge their dogma.
The Left-Hand Path completely lacks the moral imperative to FORCE others to believe as you do or suffer the consequences, which is a very important aspect - I won’t think less of anyone who thinks my values are a load of waffle, whereas, a believer usually HAS to have people see things their way. They will literally always strive for thought-control of other people.
And the LHP I practice also lacks the ability to set atrocities in motion, and then to “pass the buck” and claim that we only burned these thousands of people alive because it was written in a book, we only beat our children and wives because we’re told to do so, etc.
We retain 100% of the responsibility for our acts, there is No higher authority, and that’s why knowing what you’re against, and also, what you’re for, is vitally important IMO - if you don’t know who you are, you won’t know what you want, and then if you don’t know that, what’s even the basis for practicing magick? 
What a wicked intolerant white demoness am I.
