this is such a hard question to answer anonie you had me spiralling lol since i go BOYFRIENDS about whatever they do it was really hard for me to come up with one moment so i'll have to expand it to three sorry:
1- witayiflihartl
this one is a must you can't go without knowing felix confessed his love for hyunjin out of the blue and the part that gets me the most is "it is too much that i sometimes need to calm down, lets naturally be good friends" there is so many layers to this
2- hyunjin in the last day of 5th fanmeeting
him getting really emotional while performing felix's song and pointing at the camera in "i just wanted you to know how much i love you so" cause felix was watching and saying "i'll take unfairness of your life you live life is good" in front of everyone even though he already messaged this to felix he just wanted everybody else to know how important felix is to him
3- hongkong concert shower
you cant not see the love in this moment they were so immersed in each other everybody else disappeared for a moment their closeness and hyunjin's face says it all

if they don't see it after all this they simply don't know what being in love looks like lol