The rules are quite concise on this subject. Here are the two passages on Octagon Control and Aggression from MMA's Official Unified Rules:
Fighting area control is judged by determining who is dictating the pace, location and position of the bout. Examples of factors to consider are countering a grappler's attempt at takedown by remaining standing and legally striking; taking down an opponent to force a ground fight; creating threatening submission attempts, passing the guard to achieve mount, and creating striking opportunities.
Effective aggressiveness means moving forward and landing a legal strike or takedown.
The emphasis above is mine. The first example of demonstrating Octagon Control clearly defines that countering the takedown attempt and throwing any legal strike puts the defender in control. It's really that black and white and should be enforced as such.Effective aggressiveness means moving forward and landing a legal strike or takedown.
Another common misconception is that, even if a takedown is unsuccessful, the aspiring fighter is still rewarded more than the defender because his actions are inherently aggressive (see: Diego Sanchez vs. Martin Kampmann).
That is doubly incorrect: the measure for aggression insists that the fighter must be moving forward and landing a legal strike or takedown and, even if it did count, Octagon Control is still prioritized higher than aggression and would rest with the defender.
Therefore, a fighter that stuffs a takedown and exhibits any degree of counter striking is the one dictating the pace, location and position of the bout and is meeting the requirements for Octagon Control. An act of aggression must be effective for it to score accordingly, and success with either a strike or a takedown is an inarguable qualification for effective aggression.
There are many aspects of combat and the unified rules that offer a wide range of subjectivity and can be interpreted differently. This is not one of them.