Wyll: he was 17, when he made the pact and he had to decide on the spot. Lae'zel comes from a culture that sees killing as a necesseity, which kind of makes sense, since they are fighting a pretty powerful foe. SHe learns throughout her journey though and can become a bitter person. Shadowheart was brainwashed and you can help her get out of it. SHe is the classical cult victim.
But this is what's a huge problem for me. Everyone's a "victim" (emphasis on the quotation marks). And personally I am super-tired of people playing the "victim" card.