Der Hölle Rache at 14, a few months before his voice changed (2005)
https://www.youtube.com/watch?v=F9ijwfRTv0o (the viral video)

Hallelujah at 18 (2009)
https://www.youtube.com/watch?v=GE0uIjw20Kg

Now a bass at 22 (2013)
https://www.youtube.com/watch?v=2P2fo_RF8B0
Hallelujah
https://www.youtube.com/watch?v=BqfIXJJVlK4