Activate means to make (something) active or operative; to start or enable. This is the opposite of spoiling, impairing, or destroying effectiveness.
Why the Other Options Are Not Correct:
Debase: Means to reduce something in quality or value; to corrupt. This is a synonym for Vitiate.
Avenge: Means to inflict harm in return for an injury or wrongdoing. (Unrelated.)
Offend: Means to cause to feel upset, annoyed, or resentful. (Unrelated.)