Definitions in relation to their use in these kangaroo words, taken from Google Dictionary, and edited for formatting.
Kangaroo word: wonderful
Joey word: woeful
wonderful (adjective): inspiring delight, pleasure, or admiration; extremely good; marvelous.
woeful (adjective): characterized by, expressive of, or causing sorrow or misery.
The letters W, O, E, F, U, and L found within the anti-kangaroo word “wonderful” arrange in the listed order to complete the joey word “woeful”. While a word can have multiple definitions, in relation to their use with kangaroo words, these two words share an opposite meaning: pleasure vs. sorrow.