Is one who made another fall in love with him, then repented, considered sinful and an oppressor, while the other party still loves him and commits sins because of him?

If a person enticed another into a sinful relationship, he is a partner in the sin for causing it. A Muslim is forbidden from assisting in sin, as Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." And whoever calls to misguidance, will bear sins like those who follow him. The person who went along with it is the one who brought harm upon himself, and has no claim against the instigator. This person has done well by repenting and ending the relationship, and there is no sin upon him for the other person's persistence or what he commits due to this persistence.