Turn-off: Someone who can't communicate, narcissistic, no sense of humor, no empathy/sensitivity.
Turn-ons: The opposites of all those things. And that we just "get" each other.

Turn off...No humor and overly sincere.
Turn on...Humor, chemistry, and a face I can't take my eyes off of.

Physically?

Turn off: being sloppy or not putting any effort into your appearance. I don't expect expensive name brand clothing but buy something that fits you and isn't dirty. Don't show up for a dinner date in a hoodie.

Turn on: obviously the opposite of the above but also being able to make conversation. I'm pretty chatty but even I can't work with someone who only gives 1 or 2 word responses.

Using a picture from an advertisement as a profile photo is a big turn off.