Educate me on scummy thrash metal.

[leatherface]

Devastation- Idolatry

Deathwish- Demon Preacher

[Circlepit]

The first few Sodom albums are the best ones for me when it comes to that thrash sound bordering on black or death metal.
I'm a bit biased as I think the early Sodom releases are better than Destruction and Kreator combined.
Having said that I've giving very little time to Destruction.
Are Nifelheim thrash? I've never really listened but I'm sure I'm missing out.

[Anvil]

Devastation- Idolatry

Deathwish- Demon Preacher

Deathwish are great, both Demon Preacher and At the Edge of Damnation are killer albums. 

There is a US Blackened Thrash band called Sauron.  Only heard one of their albums, Thrash Assault, but it is vicious. 

[hellfire]

Deathrow - Raging Steel

[leatherface]

Devastation- Idolatry

Deathwish- Demon Preacher

Deathwish are great, both Demon Preacher and At the Edge of Damnation are killer albums.

Got 'Demon Preacher' recently on vinyl, wasn't cheap !

[The Wretch]

I'll definitely echo the recommendation for Razor. Literally any 80's album.

Also -

Sacrifice - Torment In Fire
Whiplash - Power And Pain
Assassin - The Upcoming Terror
Hirax - Raging Violence/Hate Fear And Power
Overkill - Feel The Fire
Holy Terror - Terror And Submission/Mind Wars
Beowülf - Beowülf
Detente - Recognize No Authority
Hallows Eve - Tales Of Terror
Znowhite - All Hail to Thee
Blessed Death - Kill Or Be Killed
At War - Ordered To Kill

Also, they are probably more speed metal early on, but definitely the s/t by Nasty Savage. And again, more speed than thrash, but I would always recommend Exciter 'Heavy Metal Maniac' 'Violence And Force' and 'Long Live The Loud' for anyone interested in that early - mid 80's period. 

[koper]

Kat - ,,Metal and Hell" or ,,666", the latter being an english version of the former. The original version sports a cheesy title, the english version is the original ponglish metal recording. Choose your poison, the music is deadly.

[open face surgery]

Loads of great recommendations but I don't know if they really fit what, I presume, you meant by scummy.

Either way, any excuse to post Infernal Majesty.

https://www.youtube.com/watch?v=9UQK70IZ6PI

https://www.youtube.com/watch?v=b1qFbtOllc4&t=47s

[Grim Reality]

Exumer - possessed by fire
Dark Angel - Darkness Descends
Death Angel - the ultra violence
Holy Terror- terror and submission
Hydra Vein - rather death than false of faith
Morbid Saint - spectrum of death
Whiplash - power and pain
Sadus - chemical exposure/illusions
Rigor Mortis - debut
Nuclear Assault- game over


Would be a few of those I go for when on that thrash buzz aside from the more typical Exodus, Sodom, Destruction, Slayer stuff...

[Mithrandir]

Check out the first 2 Mefisto demos, 2 of the best ever. In the same realm of as Obsessed by cruelty. Ancient thrashing Black/Death. Both from 1986.

https://youtu.be/4OXsi7P2QeU?si=kB_vaCmCaJo5CGm8

https://youtu.be/XH4tgcb5YGo?si=AtvQCS3C4i9kB0FD

[Ollie]

Kind of after the stuff that could be considered precursors to black and death metal but I'll check out some of those who I haven't heard yet. Cheers.

In that case you have to check out Nasty Savage. It's a terrible band name, but absolutely straddles the line between heavy thrash and proto death metal

[Mithrandir]

Loads of great recommendations but I don't know if they really fit what, I presume, you meant by scummy.

Either way, any excuse to post Infernal Majesty.

https://www.youtube.com/watch?v=9UQK70IZ6PI

https://www.youtube.com/watch?v=b1qFbtOllc4&t=47s

In my top 3 thrash records of all time.

[Ollie]

Also Face of Sin album by Mortal Sin. "I am immortal" is a stone cold classic

[Putrefaction]

Dark Angel - Darkness Descends. Album title says it all.
Exhorder - Slaughter in the Vatican. Dripping with riffs, filth and groove,  criminally underrated always.
Nuclear Assault - anything. Was my gateway band into metal.

[Mithrandir]

And of course this more recent release and an Aussie local for you,

Trench Hell - Southern Cross ripper

The only band I've ever seen do an encore of the song they opened with 

https://youtu.be/QVOAhX8_Rqs?si=D0apcMgn5w2JKUvw

Slaughter - Strappado

From 1987, Canadian thrashing madness verging on death metal

https://youtu.be/gyn9Euj58GE?si=RCPs5SnmZYYvTx8U