It depends on what origin you follow - the rebooted Sonja just has a rough start (her village being pillaged/slaughtered) and she escapes into the wild where she learns combat/survival skills & she's not visited by Scathach. She's captured later and has to fight in an arena which is where she learns her crazy fighting skills.
The original Sonja has a similar start (village is pillaged, people are slaughtered, rape, etc). After they leave, Scathach visits her and bestows unparalleled fighting skills on the condition that she would never lie with a man unless he defeated her in fair combat. I wouldn't say she's got 'super powers' - more like, she's extremely skilled but is still able to be defeated by extremely good fighters (it happens periodically).
Sick. Thanks for the info man. The Abridged Sonjapedia
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