Steven, a sexaholic who is too unattractive and undesirable to have sex, meets Liana, a fellow sex-addict who teaches other more dangerous ways to get off

I think you can shorten the redundant "unattractive and undesirable" and discard the names: "An undesirable sexaholic meets another frustrated, but gorgeous, sex addict who helps him discover more dangerous ways to get off."

If we knew more about the hook, we could add more to the logline. Interesting and racy concept, though. Questions about the genre, as it can go several ways as written (comedy, drama, mystery or horror. Good job!

Interesting logline because it has two implied goals:

- outer goal: to have sex
- inner goal: to get off

One is specific, the other not - which is normal (inner goals - or 'needs' - are rarely specific)

Now, when Steven meets Liana, his outer goal seems to be surpassed by these 'more dangerous' ways. Perhaps we need to know a little more about what this could be.

I assume the meeting with Liana is the Inciting Incident, somewhere in Act One.
For an audience to form an idea whether this movie will be worth seeing, I believe we need to have a better notion of what to expect in the second act.

In any case, I would recommend for the main character to still have a clear outer goal, even when the main goal is no longer to have sex.

I hope this helps!

Like where it's leading, yet it's a little confused - how can you be a sexaholic without having sex?? :)

You should play on Steven's level of addiction, so when Liana turns up, that's when his eyes are opened to all the new possibilities.