Is there not a contradiction between the hadiths that curse theحلَّال (one who makes lawful, i.e., by marrying a thrice-divorced woman with the intention of making her lawful for her first husband) and the one for whom it is made lawful, and the hadith that permits a woman to return to her first husband after marrying another man who divorced her after consummation?

There is no contradiction between the hadiths. Marriage with the intention of making a woman lawful for her first husband is forbidden, and its perpetrator is cursed. As for the hadith of Rufa'ah's wife, Abdurrahman ibn Az-Zubayr did not marry her with the intention of making her lawful for her first husband; rather, she desired to return to her first husband. The Prophet (peace be upon him) clarified that it is not lawful for her to do so until the second husband has consummated the marriage with her. The intention of the wife or guardian does not affect the validity of the contract; rather, the effect is due to the intention of the second husband.