I went down a rabbit hole for this exact reason last month, so I can walk you through where I’d look for the lyrics to 'Avenged Nightmare' (and how to make sure they’re actually correct).
First place I check is the obvious: official sources. That means the artist’s website, official Bandcamp or SoundCloud page, and the record label’s site or press release if there is one. If the song was released on Spotify or Apple Music, those platforms often provide synced lyrics now — I’ve found a few lines that were slightly off on fan sites but spot-on on Apple’s lyrics panel. YouTube is another good spot: official uploads sometimes include lyrics in the description or are posted as lyric videos. If you find a lyric video that looks official (good production, channel matches artist/label), that’s usually reliable.
If those don’t turn anything up, I move to community resources: Genius, Musixmatch, and (less reliably) sites like AZLyrics or LyricFind. Genius is great because of line-by-line annotations and community corrections, but always double-check who contributed the transcription. Musixmatch often syncs with players so it’s handy for listening while reading. For obscure tracks, hit Reddit, Discord fan servers, or the comments on the song release — fans frequently transcribe rarities. A tip I use: Google the exact phrase with quotes, e.g. '"Avenged Nightmare" lyrics' and include the artist name if you know it; you can also search site:genius.com or site:musixmatch.com to limit results. Lastly, if it’s a physical release, liner notes/booklets are gold for verified lyrics. If everything else fails, messaging the artist or label politely on social media sometimes gets you a straight answer — I once got a DM with a scanned booklet page, which made my week.