Sun Beast. When the Giant Sun Bear takes Radiant damage, it reduces the Radiant damage by it's Constitution modifier (2). The next time the Giant Sun Bear deals Radiant damage, but before the end of it's next turn, it deals 2 additional Radiant damage. To the Giant Sun Bear, Radiant damage and the rays of the sun are energizing.

Withering Susceptibility. When the Giant Sun Bear takes Necrotic damage, it takes additional Necrotic damage equal to it's Constitution modifier (2). The Giant Sun Bear's next attack deal 2 less damage. Because of the Giant Sun Bear's connection to the sun, it naturally dislikes necrotic energies, which seem to drain it's power.