If "never" means "not at any time," its antonym is "always."
If "never" means "not in any way," its antonym is "always," "ever," or "sometimes."
Example:
* Never will I forget your kindness. (Antonym: Always will I remember your kindness.)
* I never go to the movies. (Antonyms: I always go to the movies. I sometimes go to the movies. I ever go to the movies.)
The best antonym for "never" will depend on the specific situation.