Anything that involves deception, which unfortunately seems to be most of marketing.
I don’t mind when people just try to get their product out there, just let it be known that it exists and does X thing differently or better. I hate when they mean to deceive. Something that is intended to deceive but isn’t technically a lie is not really better than a lie, to me.
The advice I’m most scared not to follow as I get older: don’t dismiss everything that the younger generations say or do as being just a trend, and learn more about it.