Suggestions by @jacobking1

Roger Allam

as Rylanor in Warhammer 40k: The Horus Heresy (Amazon)

Score: +2

Sacha Dhawan

as Phosis T'kar in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Ace Bhatti

as Amon in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Trystan Gravelle

as "Little" Horus Aximand in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

George MacKay

as Saul Tarvitz in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Phil Dunster

as Lucius in Warhammer 40k: The Horus Heresy (Amazon)

Score: +2

Theo Barklem-Biggs

as Falkus Kibre in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Yuri Kolokolnikov

as Maggard in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Daniel Portman

as Nero Vipus in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Luke Pasqualino

as Amon in Warhammer 40k: The Horus Heresy (Amazon)

Score: 0

Staz Nair

as Hathor Maat in Warhammer 40k: The Horus Heresy (Amazon)

Score: 0

Paul Kaye

as Ignace Karkasy in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Ioan Gruffudd

as Horus Lupercal in Warhammer 40k: The Horus Heresy (Amazon)

Score: 0

Nikesh Patel

as Ahzek Ahriman in Warhammer 40k: The Horus Heresy (Amazon)

Score: +2

Rahul Kohli

as Magnus the Red in Warhammer 40k: The Horus Heresy (Amazon)

Score: +2

Freddie Fox

as Julius Kaesoron in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Richard E. Grant

as Kyril Sinderman in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Daniel Weyman

as Maloghurst in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Tommy Flanagan

as Iacton Qruze in Warhammer 40k: The Horus Heresy (Amazon)

Score: +1

Ricardo Montalban

as Rick Martinez in The Martian (1950s)

Score: +1