Use 'diametrical' to stress a complete or exact opposition between two things. Their views on the issue were diametrical, leaving no room for compromise.
Pro Tip 2/3
Beyond Differences
'Diametrical' implies more than just different opinions; it suggests polar opposites. Her minimalist lifestyle is diametrical to his lavish spending habits.
Pro Tip 3/3
Not Physical Distance
Don't confuse it with literal distance. 'Diametrical' refers to figurative or abstract contrasts. Their interpretations of the poem's meaning were diametrical.