Greek metal is traditionally raw, but also musical. Here is a link to the full album of Mentally Defiled with better sound quality, check out especially the song Beyond Redemption at 22:14, a thrash CLASSIC:
Some members of that band play in another thrash band called Violent Definition, their album has a cleaner sounding mix. Similar style, but more influenced by Razor 'Violent Restitution' / 'Shotgun Justice' era. The first song is an instrumental that especially reminds of Violent Restitution.
Interesting to hear re: Chilean thrash, any band/s in particular? I only know the old bands like Pentagram & Torturer.