Is the anterior cruciate ligament tear surgery is painful?

Yes (to an extent) Any surgery will cause post-operative pain. There will also be discomfort with the therapy that is required after the procedure. Different patients have different pain thresholds, but usually, the pain post-operatively isn't so bad (from the feedback i've gotten from my patients who have had the surgery).
Some pain expected. Most patients tolerate the acl reconstruction well. Yes it does cause some pain but only for a short period of time... This type of surgery is done as an outpatient typically and the anesthesiologist will numb up the leg well prior to the procedure which minimizes the initial postoperative pain.
Yes some. All surgery has some pain as it is an insult to the body. It is short lived and controlled by oral meds easily. U wear a brace so u r comfortable. Worth it!