Updated list November 2020, it seems to be updated infrequently with new books and new votes:
Beyond Redemption - by Michael R Fletcher, Grimdark Rating 4.66
The Darkness That Comes Before - by R. Scott Bakker, Grimdark Rating 4.52
Prince of Thorns - by Mark Lawrence, Grimdark Rating 4.42
The Court of Broken Knives - by Anna Spark Smith, Grimdark Rating 4.18
Godblind - by Anna Stephens, Grimdark Rating 4.15
The Steel Remains - by Richard K. Morgan, Grimdark Rating 4.10
The Blade Itself - by Joe Abercrombie, Grimdark Rating 4.10
Heroes Die - by Matthew Woodring Stover, Grimdark Rating 3.97 (*)
Devices and Desires - by K.J Parker, Grimdark Rating 3.89 (*)
The Black Company - by Glen Cook, Grimdark Rating 3.81
Low Town - by Daniel Polansky, Grimdark Rating 3.80
A Little Hatred - by Joe Abercombie, Grimdark Rating 3.77 (*)
Blackwing - by Ed McDonald, Grimdark Rating 3.73
The Left Hand of God - by Paul Hoffman, Grimdark Rating 3.69 (*)
Priest of Bones - by Peter McLean, Grimdark Rating 3.63 (*)
Horus Rising - by Dan Abnet, Grimdark Rating 3.60 (*)
The Grim Company - by Luke Scull, Grimdark Rating 3.55
The Mirror Empire - by Kameron Hurley, Grimdark Rating 3.49 (*)
The Poppy War - by R.F. Kuang, Grimdark Rating 3.48 (*)
Where Loyalties Lie by Rob J. Hayes, Grimdark Rating 3.45 (*)
A Game of Thrones - by George RR Martin, Grimdark Rating 3.43
Gardens of the Moon - by Steven Erikson, Grimdark Rating 3.43
Elric of Melnibone - by Michael Moorcock, Grimdark Rating 3.41
Scourge of the Betrayer - by Jeff Salyards, Grimdark Rating 3.31 (*)
The Gutter Prayer by Gareth Ryder-Hanrahan, Grimdark Rating 3.29 (*)
Prince of Fools - by Mark Lawrence, Grimdark Rating 3.27
Lord Foul's Bane - by Stephen R Donaldson, Grimdark Rating 3.19
The Vagrant - by Peter Newman, Grimdark Rating 3.11
The Emperor's Blades - by Brian Staveley, Grimdark Rating 3.11 (*)
Red Sister - by Mark Lawrence, Grimdark Rating 3.08
The Library at Mount Char - by Scott Hawkins, Grimdark Rating 2.89 (*)
The Grey Bastards - by Jonathan French, Grimdark Rating 2.89 (*)
Shadow of the Torturer - by Gene Wolfe, Grimdark Rating 2.88 (*)
Bloodsong - by Anthony Ryan, Grimdark Rating 2.88 (*)
The Girl And The Stars - by Mark Lawrence, Grimdark Rating 2.84 (*)
The Last Wish - by Andrzej Sapkowski, Grimdark Rating 2.82
The Way of Shadows - by Brent Weeks, Grimdark Rating 2.78
Traitor's Blade - by Sebastian de Castell, Grimdark Rating 2.74 (*)
Conan - by Howard, Sprague de Camp & Lin Carter, Grimdark Rating 2.68
Half a King - by Joe Abercrombie, Grimdark Rating 2.67
The Gunslinger - by Stephen King, Grimdark Rating 2.66
The Red Knight - by Miles Cameron, Grimdark Rating 2.66 (*)
The Traitor Baru Cormorant - by Seth Dickinson, Grimdark Rating 2.62 (*)
Ember In The Ashes - by Sabaa Tahir, Grimdark Rating 2.60 (*)
The Warded Man by Peter V. Brett, Grimdark Rating 2.56
The Lies of Locke Lamora - by Scott Lynch, Grimdark Rating 2.32
Legend - by David Gemmell, Grimdark Rating 2.27
The Fifth Season - by N.K. Jemisin, Grimdark Rating 2.26 (*)
Malice - by John Gwynne, Grimdark Rating 2.23
The Final Empire - by Brandon Sanderson, Grimdark Rating 1.97
Assassin's Apprentice - by Robin Hobb, Grimdark Rating 1.96
Kings of the Wyld by Nicholas Eames, Grimdark Rating 1.79 (*)
The Hundred Thousand Kingdoms - by N.K. Jemisin, Grimdark Rating 1.75 (*)
The Innocent Mage - by Karen Miller, Grimdark Rating 1.54 (*)
The Sword of Truth - by Terry Goodkind, Grimdark Rating 1.51
Magician - by Raymond E Feist, Grimdark Rating 1.46
One Word Kill - by Mark Lawrence, Grimdark rating 1.42 (*)
The Pawn of Prophecy - by David Eddings, Grimdark Rating 1.26
The Sword of Shannara - by Terry Brooks, Grimdark Rating 1.16
(*) Average based on fewer than 100 votes