When I first played 2 I thought Demyx then I after I beat it I was bored so I went to Hollow Bastion/Radient Garden & was just wandering around then saw Sephiroth, talked to him & went into a battle, he is the hardest boss
I haven't played Re:Com but I have played Com, I say there both as good as eachother because one you can carry around & the other you get a more detailed look at things