She liked the painting at first glance.
一目見ただけで、それが偽物だとわかった。
I could tell it was a fake with just one look.
complete view; bird's-eye view
A view that takes in the whole scene at once; often used with 一目に見渡す or 一目で見渡せる.
山頂から町を一目に見渡せる。
From the mountaintop, you can get a complete view of the town.
It was clear at a glance that he was the culprit.
From the observation deck you can take in the whole city at a glance.
Everyone holds his skill in high regard.
一目 just means 'a glance' or 'one look', whereas 一目惚れ adds the specific meaning of falling in love from that single glance.