A few users were discussing powerful vocals, and in my opinion, the only Vocaloids capable of singing with serious power are Meiko, Miku, Rin/Len, Kanon, and Cul. I've never found a western VB that can sing powerfully. It's a bit disappointing for me that most Vocaloids and VB's are soft, but I like the soft ones too so I don't complain much.
That said, another unpopular opinion I have in the vocal synth fandom and music scene in general is that powerful singing is not needed in rock. I compose in doom metal where soft singing, powerful singing, screaming, and speech are all common and all often buried under guitars that sound like chainsaws moving at the glacial pace of certain doom, so I never worry about a synth being too soft for my music.
This would probably be a popular opinion on a doom metal board if vocal synths were popular in doom metal, but unfortunately they are not popular there.