I wouldn't call Samus well written. When retroactive put bounty hunting sidequests in Metroid prime, Nintendo was confused why Samus would be hunting people. Turns out when Nintendo(Japanese) originally said she was a bounty hunter (in english), they didn't actually know what it means, they just thought it sounded cool. According to nintendo the reason Samus does what she does is because of a "motherly love" for humanity. So basically, samus' motivations boil down to hormones.