Answer:
The word in the sentence which functions as an objective complement is the following one:
dangerous.
Step-by-step explanation:
Check it out:
The meteorologist considered the impending storm dangerous.
 ↓ ↓ ↓ ↓
 subject verb direct object objective complement
If we ask the question: "What did the metereologist consider?", the answer is: "the impending storm", which is the direct object. 
If the question is: "What did the metereologist consider the impending storm to be like?", the answer we get is: "dangerous", which appears right after the direct object and refers to it. In other words, it complements it.