Thanos weakness is "A subconscious desire to lose." this means Thanos arranges for himself to defeated because deep down he knows he doesn't deserve to win. Thanos want's his death to be an honorable one at the hands of a worthy adversary.
Additional Infinity Gems allow him to control Rhythm, Matter, and Egos, but the Infinity Gauntlet can only hold six Infinity Gems at a time so it deepens on which Gems he happens to carry.