That's a complete sentence. I've got troubles understanding what parts of speech are. According to my dictionaries:
阳光 - sunshine,
格外 - especially,
刺眼 - to dazzle.
So the sentence would mean "The sunshine outside the bus was extraordinarily dazzling".
But... There's the second 的 in this sentence (阳光格外的刺眼). And objects which go after 的 are nouns (from what I know). So 刺眼 turns to be a noun? If so, where's the verb in this sentence? I really don't understand this 的. I'd gladly put 地 instead.
This is 100% clear: 车外的阳光. The unclear 的 is here: 阳光格外的刺眼.