All of them can become valuable if a particular end user likes them. But I think it is too soon for keyword1keyword2 in 2017 to get some real action. On the other side, they are for standard renewals, and if you can keep them in your portfolio using renewal promotions, they eventually can get profitable.
(You can PM me, I can give you some tips).
But consider also this:
- you have around 30 000 dictionary words you can give in front of .online, and names will make sense
- you have around 200*30 000 names you can create when registering keyword1keyword2 domains
(200 is number of various adjectives, or verbs, very rough estimate, but it can give you an idea...).
So if you can, try to get keyword1 form to your portfolio - I guess you will be much more happy with the overall results
