Rebellion, ambition and obsession….!
Thank you for asking such a lovely question.
If Shani is the lord of Justice, Rahu is the lord of rebellion ambition and obsession.
The story of Rahu goes back to ancient times when after the churning of ocean, the nectar of immortality, named Amrit was obtained. Gods and demons were fighting over it.
Lord Vishnu intervened in the form of the most beautiful woman in the universe, MOHINI and offered to solve the dispute. Mohini bewitched the demons with her beauty and tricked them by serving them the poison and giving Amrit to the gods.
However the Demon named Swarbhanu was obsessively focused on his goal of getting Amrit. And he was the only one who realized what was going on, he switched to the side of gods and managed to fool even Lord Vishnu and get Amrit.
Sun and moon intimated Lord Vishnu who immediately cut the head of Swarbhanu but by then he had swallowed the Amrit, hence had become immortal.
The head became Rahu and the tail became Ketu. While he was behaded, he was awarded position and power of planet for his focus and hustle.
So Rahu is the eternal rebel who wants what he wants and when he wants. He is willing to challenge the system, society and powers that be.
The greatest rebel of all times was Rahu who rebelled against Vishnu Himself and reached his goal with an obsessive streak.
Rahu is not just a harsh planet. It has a great side too.
The eternal rebel Rahu gives rise to REBELS whenever rulers become corrupt, these rebels throw down the corrupt sun.
All that desires are ruled by Rahu. All the progress that we see today, is a result of Rahu.
Even the Internet which enables you to read this answer, is powered by Rahu.
Guess we have to thank him. Thank you Mr. Rahu.
G. Vijay Kumar