Though Iago does kill when he stabs and murders Roderigo, he created most of his devastation through the use of others who unwittingly follow their own agenda which Iago subverts to achieve a web of events which succeeds in making Cassio first lose his position as Othello's lieutenant, then petition Desdemona to be reinstated which allows Iago to suggest Desdemona's adultery and later to motivate Roderigo to kill him (Cassio).
Iago's character is complex, but in Act I, Scene I, where he describes his disgust at being overlooked for Othello's lieutenant, we can see that a primary motivation for Iago's skillful manipulations was revenge and anger; revenge for Cassio replacing him, anger that Othello overlooked him. Thus it can be seen that Iago's manipulations are driven by a basic desire to avenge those who hurt him but also to gain what he believes is his, indeed Iago's suggestion that Cassio and Desdemona are having an affair earns Iago Othello's trust and the position as his lieutenant in Act III, Scene III.
However being made lieutenant only satisfies his pride, his continuing with his plan to discredit Desdemona shows us that it is not enough for Iago to have what he believes is his, he must punish Othello for overlooking him in the first place by making Othello disbelieve and destroy his virtuous wife...
Iago is pragmatic. We see this in the manner in which he uses opportunity to aid his plan to hurt Cassio and Othello. When Iago realizes Cassio's admiration of Desdemona, he immediately formulates a plan to use this to make Othello suspect adultery.
Though Iago appears to have the goal of misery for Othello and Cassio, he does not appear to have a specific detailed plan, he continually refers to using insights he makes about Cassio, Othello, Roderigo and Desdemona to further his plan in his asides in the play.
Iago's pragmatism is also evident in his use