The Deepest
Noun, な adjective, and の adjective
さいしん
日本で最深な地下鉄は、地下48ｍの場所がある大え戸線です。
Japan's deepest subway line is the Oedo line, which goes as low as 48 meters below ground.
しっとは人間の最深のつみだ。
Jealousy is the deepest sin of human sins.
サーモンと俺は、光が到達できる海の最深部に位置するロマンチックな秘密の洞穴で、結婚式をあげた。
Salmon and I had our wedding ceremony in a romantic hidden cave located at the deepest part of the ocean that light can still reach.
The most deep is the deepest.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.