Dealing with enemies and dealing with nemeses are completely different situations.
When dealing with an enemy, one calculates the gains and losses, weighing whether defeating the enemy is worth the cost. If it's not worth it, then there's no need to take action.
In the case that the enemy is too strong, there's even less of a reason to make a move.
Although Sun Wukong was very brave, he was not a foolhardy man. He dared to attack Wutian Buddha because of his ignorance of the fear.
However, once Jiang Liu informed Sun Wukong of the Wutian Buddha's strength, even surpassing Tathagata by half a step? Sun Wukong immediately backed down, with no intention of making a move.
If one cannot win, then why rush to engage?
But when it comes to a nemesis, there is no need to consider gains and losses.
If there is a grudge, then one will naturally seek revenge at all costs.
For example, Sun Wukong harbored hatred towards Tathagata for his betrayal and deceit from the past.