The two biggest disappointments for me are...
Alcest - Les voyages de l'âme
After two incredible albums in Souvenirs d'un Autre Monde and Écailles de Lune this came as a big disappointment. It just sounds so bland and flat compared to the other two albums. Mind you I gave it a chance and listened to it a few times, but there is just nothing memorable going on here.
A Place To Bury Strangers - Worship
Pretty much the same story as Alcest, two great albums and then this. Again it sounds bland, safe and unadventurous compared to their other two albums and just doesn't hold up. Their self-titled and Exploding Head sounded dark and dangerous but you don't get any of that on Worship, instead you get an album that could have been made by countless other bands.