True gaslighting.is systematic. It's akin to emotional/mental/pychological torture. It's goal is to break your mind or at the very least to make you think your perception is so faulty that you can not trust it. You come away believing that you are insane.
Denial is very close. Denial is often the prerogative of weak-minded people who don't want to face things and so they pretend things are different than they are.
Long term denialists do induce a type of gaslighting effect. But it is not quite the same as a true gaslighter.
Gaslighters will be utterly invested in destroying your reputation too. Usually to cover their own crimes against you. And in an exploitative way.They will have everyone doubting your grip on reality.
My ex went as far as to scream at me for hours, right up into my face, that I was crazy, in front of our children.
That is very overt, often it is more subtle than that.
Another thing he would do when I tried to call him on his behaviour, was to deny it by saying "paranoid delusions."
Gaslighters don't just minimise to avoid dealing with uncomfortable emotions, they flat our deny that something ever happened.
They will treat you in a sick, pathological way; cruel and utterly lacking in empathy and then tell you that "no, it is you that has the problem".
Example: my ex told my kid"s doctor that I was a "psychopath". I know because she was so concerned she rang me up and told me.
This was one of the clues for me, because although I believed I must be "crazy", I knew that there was no way that I was a "psychopath". If anything, I'm overly empathetic, and manipulatable as a result (not so much anymore, I've had a lot of experience with manipulators now, I could practically write a book on their ploys). I left him not long after this happened.
Eventually I turned the tables on him by saying "ok, I'll get some help". I went out and sought counselling. He didn't want that. He just wanted full control of me and everything that was mine. And to get paid for it. He claimed a "carer" pension for me, yet treated me as a slave.
Deliberate sleep deprivation is another favourite of full-blown gaslighters, as is drugging. My ex did both.
For over 20 years. He kept me trapped because he told me, over and over again " if you leave, you won't get the children, because you are crazy." Of course I believed him, he was good at it.
A good gaslighter will actually achieve their aim and turn you into a complete nervous wreck who believes %100 that they must be insane.