Iago conveys, especially in Act 1, scene 1, that he will put on a fake demeanor with Othello so that Othello unequivocally trusts Iago.
The first example is when he is talking to Roderigo about how much he hates "the Moor." Through the derogatory language, it is unclear whether Iago hates him for his race in addition to other qualities or if he uses the derogatory language because he hates Othello.
"In following him, I follow but myself.
Heaven is my judge, not I for love and duty,
But seeming so, for my peculiar end.
For when my outward action doth demonstrate
The native act and figure of my heart
In compliment extern, ’tis not long after
But I will wear my heart upon my sleeve
For daws to peck at. I am not what I am" (I.i.60-67).
This quote shows that Iago is following himself and acting not what he is. After speaking with Brabantio (without revealing his identity), he runs off to be with Othello so that Othello does not suspect Iago for snitching on him to Othello.
The second example of Iago telling the audience that he is not acting on his true feelings is at the end of Act 1 when his plan to ruin Othello's reputation fails. Iago hoped that Brabantio could bring suit to the court that Othello stole Desdemona, but the Duke sides with Desdemona and Othello. In response, Iago does not seem disheartened. Instead, he has a new plan ready to go. He decides to make Othello feel betrayed by Cassio causing tension, anger and extreme action. Iago says
He holds me well.
The better shall my purpose work on him
This quote shows that Iago purposefully will lie and act like Othello's willing and loyal advisor in order to gain his trust. This trust will help him exact his revenge later on. These actions show Iago to not be just a physically dominant, angry soldier, but rather a smart, conniving and manipulative man. These actions are the actions of a true villain that does nothing to get pitied.