I've chased this exact lyric before while trying to ID a song from a playlist, and honestly the phrase 'I love you most' shows up in a surprising number of tracks across genres. It crops up in indie ballads, churchy hymns, country slow dances, and even some children's lullabies, so knowing only that line can be a little like finding a seashell on a big beach — possible, but you need more context.
What helped me most when I was hunting was narrowing things down: where did I hear it (radio, movie, café), was the singer male or female, roughly when was the song made, any other words or melody bits I remembered. Then I ran a few searches with the exact phrase in quotes, checked lyric sites like Genius and Musixmatch, and used a snippet search on YouTube. If you can hum it, try Google’s hum-to-search or SoundHound. If you want, tell me whether it was upbeat or slow, and a line that might come before or after 'I love you most' — with one extra word the search gets so much better, and I’ll happily help dig through likely matches.