The phrase 'not at all friendly' is correct and usable in written English.
You can use this phrase when you want to emphasize the fact that something or someone is unfriendly. For example: "The receptionist I met was not at all friendly."
The ministry described the meeting as a "unilateral move which is not at all friendly toward our country".
The majority of the boys probably envied my 6-foot-4-inch height but were not at all friendly to a newcomer from the wild West.
Nevertheless, the city was soon caught up in a not at all friendly debate of the only-in-Madison variety, a controversy that in its most heated moments succeeded in overshadowing the national crisis that had provoked it.
Two other famous "permabears," Charles Allmon of Growth Stock Outlook and Richard Russell of Dow Theory Letters, are still not at all friendly.
"Bob Saget: That's What I'm Talkin' About" showcases the comic and former "Full House" star in a not-at-all family-friendly stand-up special.
Even if you weren't at all friendly with a particular person -- well, for example, I was part of a serious, sort of hippie fringe crowd in high school and Steve was the kind of guy who knew everyone and had lots of friends; we barely spoke in high school, but now, through the ibook, we're very, very friendly and I've even hired him to do some work for my company".
— Arles is just the opposite: not at all car friendly.
Ours was not at all a friendly relationship.
It was just kind of a pain, and not at all user friendly.
We are back in River's night-time city: the London where he lives is mostly dark, jewelled with tiny lights, but it doesn't feel at all friendly.
A new mayor has come to office and he is now getting to work on the Han river, an important river that is not at all pedestrian-friendly.
