To what extend can we argue that iago has the weakest personality.

In that case, I don't agree, Iago's purpose and overwhelming purpose in the play is to disrupt Othello's life..... to ruin him. Iago is a master manipulator, he moves the plot along, and he supplies the audience with information. In fact, Iago does a great deal of character analysis and exposition for the audience. "These fellows" that flatter for their own purposes "have some soul," Iago says (I.i.54). Contrary to his underhanded self-flattery, Iago seems to have no soul; he never repents, never lets up with his schemes, and never seems to tire of the damage he causes. His statement, "In following [Othello] I follow but myself" emphasizes that he is acting completely out of his own self-interest (I.i.58). Iago will thus hide his motivations and convey only falsehood. If he were to "wear [his] heart upon [his] sleeve", he would be torn apart (I.i.64). Honesty would destroy him.

Even when he is at his most honest, in this scene with Roderigo, Iago misrepresents just how evil he truly is. Iago parallels another Shakespearean character, Richard III, in his self-awareness of his villainous character, and lack of remorse and use of false representations. In this first scene, Iago has foreshadowed the great deceptions that he will engineer.

For additional information, follow the link provided below and check out the analysis for each scene in Act I.