For me, ruthless route was very hard to deal because of I've beforely played the nice/romantic route, and my brain betrayed me, imagining mister Blas Garcia's voice as Asterion's (I recommend you watch the scene Tai Lung vs Shifu in Kung Fu Panda dubbed on Mexican Spanish). I've unlocked 3 ending, and wow, that's a very good way to explore Argos' story and his legacy. I hope to discover the fourth one.
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It's better a reply than an edit. I unlocked all 4 endings, now I can't stop searching for Argos' true identity in the main route in other backgrounds. He is a good snakeman, and I loved how he develops himself in both main and ruthless routes. The hardest ending to find, for me, was Asterion's ending