Are there any novels on Novelblur that feature a protagonist who is secretly powerful but hides their abilities, perhaps due to betrayal or a desire for a quiet life?

Yes, Novelblur has several novels that explore the theme of protagonists hiding their true strength. "The Glitched Mage" is a prime example, where Riven's life was a sacrifice, and he was betrayed and broken. This betrayal seems to awaken a hidden power within him, suggesting he might have been holding back or was underestimated. The description hints at a shattering of a world of magic and monsters, implying his revealed strength will be significant.

Another novel that touches upon this is "I lost my Copy System and awakened a Plundering System." Draco Xandros initially had a powerful Copy System but was stripped of everything by a devastating betrayal. The awakening of a Plundering System suggests a new path to power, and it's highly probable that he will need to conceal his newfound abilities or operate from the shadows as he rebuilds or seeks revenge. While not explicitly stated as hiding abilities, the context of betrayal and loss often leads to protagonists becoming more cautious and strategic about revealing their full capabilities.