exasperatingly

Exasperatingly describes something done in a way that causes intense irritation or frustration.

It emphasizes the effect on the observer rather than the intent of the actor: The train was exasperatingly slow.

Something exasperatingly difficult pushes past mere challenge into the realm of wanting to throw your hands up.

The word often appears with adjectives to amplify annoyance: exasperatingly vague, exasperatingly stubborn.