Final answer:
Without the specific context or content from the original work, the question about the character who has changed the most by Christian's death in Act IV cannot be accurately answered.
Step-by-step explanation:
The character who has undergone the greatest change by the time of Christian's death in Act IV can be interpreted from various contexts, but is not explicitly outlined in the provided materials. To determine the character who has undergone the greatest change, one would typically analyze their development throughout a narrative. Given the disjointed excerpts and lack of specific reference to Christian or Act IV in the provided text, we cannot accurately answer who has changed the most without additional context or content from the original work in question. The information pertaining to early Christianity and figures such as Saint Paul and Thecla, while rich in historical and thematic value, does not directly relate to the transformation of a character in a specific act of a play or literary work. Therefore, without additional context or referencing the specific act and surrounding circumstances of Christian's death within that narrative, providing an informed analysis of character transformation is not possible.