Suggestions by @christopherrowe

Tom Hiddleston

as God Of Death in UNDERTALE

Score: +1

Jacob Tremblay

as Asriel in UNDERTALE

Score: +3

Chris Evans

as Asgore in UNDERTALE

Score: -2

Kristen Schaal

as Alphys in UNDERTALE

Score: +1

Scarlett Johansson

as Undyne in UNDERTALE

Score: +1

Jessica Chastain

as Toriel in UNDERTALE

Score: 0

Simon Pegg

as Flowey in UNDERTALE

Score: -2

Finn Wolfhard

as Chara in UNDERTALE

Score: +2

Millie Bobby Brown

as Frisk in UNDERTALE

Score: +1

Jim Carrey

as Papyrus in UNDERTALE

Score: +4

Benedict Cumberbatch

as Sans in UNDERTALE

Score: 0

Patrick Stump

as Composer in Undertale

Score: +1

Brendon Urie

as Mettaton in Undertale

Score: +1

Edgar Wright

as Director in Undertale

Score: +1

Chris Evans

as Asgore in Undertale

Score: -1

Joaquin Phoenix

as Napstablook in Undertale

Score: -1

Scarlett Johansson

as Undyne in Undertale

Score: +1

Finn Wolfhard

as Frisk in Undertale

Score: 0

Simon Pegg

as Flowey in Undertale

Score: -1

Jim Carrey

as Papyrus in Undertale

Score: +5