Warning! Spoilers ahead for Berserk chapter 360!
The anti-hero Guts performs a litany of heroic feats throughout the late mangaka Kentaro Miura's epic Berserk manga, most of which involve cutting down massive demons or a large number of warriors with his massive blade while donning the pain-defying Berserker armor. But most fans forget about one of his most impressive deeds because it's less bloody (though the spilling of blood did help). It was how he played a major role in converting the God-fearing and heretic-burning Lady Farnese to a witch who helps others.
Before meeting Guts, the Lady Farnese's faith in the Holy See was unwavering and she took a sadistic pleasure - even experienced arousal - when punishing heretics. All of that changes when she becomes Guts' captive on two separate occasions. Lady Farnese's captivity exposes her to the nightly horrors that Guts is perpetually subjected to as a result of him being a sacrifice of the Eclipse, during which she witnesses how Guts places his life in his own hands rather than relying on religion. This moves her to such an extent that she gives up on her faith and everything she knows to travel with him.
Lady Farnese's travels with Guts in the Berserk manga initially have a negative effect on her as the amazing abilities of her companions only accentuate her own uselessness by comparison. But Lady Farnese later comes to serve as the official protector of Guts' lover Casca and connects with her so well that Guts can't ignore her usefulness and praises Lady Farnese exceedingly. The resulting rebound effect she experiences drastically empowers Lady Farnese, causing her to embrace this new role as Casca's guardian with great fervor. This eventually leads to her exploring magic, something she once burned those she suspected of practicing.
How much Guts impacts Farnese is summarized quite thoroughly by her family's trusted servant and Lady Farnese's illegitimate brother Serpico in chapter 349. Serpico essentially views his sister as a better person because she can now stand on her own, thanks to Guts. She has a purpose in life for the first time since she has someone to protect: Casca. Some might view how much Lady Farnese's transformation is reliant on Guts as a weakness. But he just gave her the push she needed to get a jump-start on her new life. In fact, Farnese later plays a pivotal role in making Casca more self-reliant and therefore no longer dependent on her when she helps reassemble Casca's broken mind in her dreams. The entire basis of Farnese's new identity is contingent on how much Casca depends on her, and the fact that she still willingly does what she can so that Casca can function on her own shows incredible strength in character. Lady Farnese, however, finds a new purpose in chapter 360 when she starts to master her powers in record time even though she started practicing witchcraft much later in life, becoming a powerful witch in her own right and no longer having to depend on another's weakness to make her strong.
Before meeting Guts in Berserk, Lady Farnese found meaning in a religion that brought out her worst qualities by torturing those whom she suspected of witchcraft. It is Guts' ability to place absolute trust in himself instead of a deity that helps Farnese reject everything she knows and immerse herself in a new life of danger, where her self-worth soon comes from helping others. Lady Farnese's strength quickly grows to such an extent that she is able to provide those who gave her meaning with the ability to function on their own even though she could lose her worthiness, potentially rendering herself meaningless, though she unearths another power inside of her that makes her self-reliant. In another impressive change in character, Lady Farnese's journey with Guts leads to her embracing the very magic she once viewed as heretical, proving she is capable of realizing her past faults and pursuing a way of life that can help others, even if it means proving her former life was a lie.