Disillusion (verb)

1. To free from false beliefs or illusions.
2. To cause to lose faith or hope.
3. To disappoint by revealing the true nature of something or someone.

Origin:

Late 19th century, from dis- + illusion.

Examples:

1. The harsh reality of the world disillusioned the young idealist.
2. The failure of the project disillusioned the investors.
3. The truth about the leader's past actions disillusioned many of his supporters.
4. The disillusionment with the government led to widespread protests.
5. The disillusion with the product was reflected in the decrease in sales.