Admittedly, most of what I know about this comes from William Morris's "The Defense of Guenevere," but I was under the impression that
Maleagant was one of those conniving, cowardly villains who were extremely weak when confronted directly.
His whole shtick was that he kidnapped Guenevere, relying on his magic castle to keep him safe, and when Lancelot persevered, it was only Guenevere's intervention that saw Maleagant being spared. Later, when he tried to spill the beans about Lancelot and Guenevere having an affair, Lancelot challenged him to a duel, and he only agreed under the stipulation that Lancelot would fight with no helmet, the left half of his torso unarmored, and his left hand tied behind his back (i.e. unable to use a shield). That Maleagant
still lost struck me as a testament to his own weakness as much as Lancelot's strength.