Ravana was so powerful that Lord Vishnu himself had to incarnate as Shri Ram to defeat him. But did you know that during the Ramayana era, there were two other warriors besides Lord Ram who possessed the full capability to slay Ravana? These warriors were none other than Mahabali Hanuman and the Monkey King, Bali.
Hanuman's power was limitless. When he reached Lanka, he was capable of destroying the entire city and slaying Ravana all by himself. He chose not to do so only because he had not received the command from Lord Shri Ram to kill Ravana. Since he was solely on a mission to find Mother Sita, he strictly adhered to his discipline and followed his master's orders.
Bali received a unique boon from Lord Brahma: whoever came to fight him would lose half of their strength to Bali. Once, when the arrogant Ravana arrived to challenge Bali, the king was absorbed in his prayers. When Ravana continued to disturb him, Bali simply tucked Ravana under his arm (armpit) and carried him captive while circumambulating the four oceans. Bali's speed was so great that he kept Ravana trapped under his arm until he completed his rounds and offered Arghya to the Sun. Had Bali wished, he could have ended Ravana’s life at that very moment.
Ravana's end was not caused by a lack of physical power, but by his ego. He believed that no one could defeat him, and this very arrogance ultimately became the cause of his death.