I'm afraid of the treatments for legionnaires' disease. Are they dangerous?

No. Any medical treatment has a potential for complications. Drugs (medication) work well, but no matter what you use (even aspirin) there are potential side effects that are unwanted or undesirable. The downside of no treatment is usually less than the downside of treatment complications/side effects.
No. L can kill you antimicrobials can save your life side effects of the medication are very rare.