Suggestions by @cocona

Jordan Calloway

as Viktor Krum in Harry Potter (all black cast)

Score: +1

Corbin Bleu

as George Weasley in Harry Potter (all black cast)

Score: 0

Brandon T. Jackson

as Fred Weasley in Harry Potter (all black cast)

Score: +1

Brandon T. Jackson

as Fred and George Weasley in Harry Potter (all black cast)

Score: +1

Taraji P. Henson

as Narcissa Malfoy in Harry Potter (all black cast)

Score: +1

Jesse Williams

as Lucius Malfoy in Harry Potter (all black cast)

Score: 0

Cassie Ventura

as Cho Chang in Harry Potter (all black cast)

Score: 0

Michael B. Jordan

as Cedric Diggory in Harry Potter (all black cast)

Score: +2

Michael B. Jordan

as Cedric Diggory in Harry Potter (all black cast)

Score: +1

Lil Rel Howery

as Petter Pettigrew in Harry Potter (all black cast)

Score: +1

Regina Hall

as Nymphadora Tonks in Harry Potter (all black cast)

Score: +1

Jamie Foxx

as Remus Lupin in Harry Potter (all black cast)

Score: +1

Denzel Washington

as Sirius Black in Harry Potter (all black cast)

Score: +1

Will Smith

as James Potter in Harry Potter (all black cast)

Score: 0

Zoe Saldaña

as Lily Potter in Harry Potter (all black cast)

Score: +2

Alfre Woodard

as Bellatrix Lestrange in Harry Potter (all black cast)

Score: 0

Samuel L. Jackson

as Lord Voldemort in Harry Potter (all black cast)

Score: -1

Tyler James Williams

as Neville Longbottom in Harry Potter (all black cast)

Score: +2

Ving Rhames

as Rubeus Hagrid in Harry Potter (all black cast)

Score: +1

Viola Davis

as Minerva Mcgonagall in Harry Potter (all black cast)

Score: +1