Uncertain. Tyrant could possibly win but there's no indication he's had as much exposure to magic as Galactus has had (Agamotto, Mephisto, Strange) and that does play somewhat of a factor since G resorts to satiating his hunger when he's combating things he doesn't understand (since he is a creature of science).
By correlation Tyrant-a product of Galactus' science-is himself a creature of science...does he have as much experience with magic as big G...uncertain. Probably not
Dormammu 5.5/10