いよいよ

いよいよ
adverb
finally; at last; more and more
1. finally; at last; at long last
Indicates that something anticipated is about to happen or has begun.
This is finally the real thing.
The new semester finally starts tomorrow.
After long preparations, the opening day has finally arrived.
2. more and more; increasingly
Indicates that something is intensifying or becoming more pronounced.
The rain has become increasingly intense.
The situation is becoming more and more serious.
Autumn has deepened, and it's getting colder and colder.

TWO MAIN MEANINGS:

1) "Finally/at last" - Used when an anticipated moment arrives

2) "More and more" - Indicates intensification

NUANCE: Often carries a sense of anticipation, excitement, or urgency. Can imply that something important is about to happen after a period of waiting.