Riz Ahmed did not receive an Oscar nomination for portraying Omar in Four Lions.
Riz Ahmed who seems to be slowly breaking out, most notably with his very dramatic role in the mini-series The Night Of, despite being a terrorist leader this is not dramatically minded role...for the most part. Ahmed instead plays essentially Moe Howard of the Three Stooges as the "brains" of a group of the dimwitted fanatics. Ahmed's performance is therefore to be the wrangler among the group more or less. Ahmed's performance is interesting in turn, like Moe Howard actually, he has to be sort of the straight man but also comedic in his own way as well. There is much of it as purely the Moe of the group in terms of dealing with the overt stupidity of the rest of the group particularly the constantly angry convert Barry (Nigel Lindsay) with a varied amount of dumb ideas on how they should go about being a terrorist cell. Ahmed brings the right type of exasperation in every little reaction to this, but also the more direct vicious anger proper for a Moe Howard type. He's especially hilarious when he breaks down Barry's idea of bombing a mosque to the moderates to become radical, as Ahmed brings nothing but the most extreme disbelief and derision in every breath as he explains how stupid the idea is.
He's also the straight man to the other idiots in the group though Ahmed brings as much of a certain confusion towards their incompetence he handles it a bit differently particularly towards the simpleton Waj (Kayvan Novak). It is here though he is again the Moe as he has to wrangle them towards the cause though again Ahmed portrays a certain way. This is very important in terms of maintaining the tone of the film as Ahmed never portrays Omar, the most competent of the men, still realistically as a jihadist. When Omar goes about encouraging, or really manipulating, the other men Ahmed doesn't bring the passion of a true fanatic, as that really wouldn't be funny. Ahmed instead approaches it basically as a guy trying to almost form kind of a band, a band he takes seriously yet can't quite get his guys to work properly together. He doesn't deliver his words to them as these passionate views of a mad man, but rather of a fairly stressed out guy just trying to make what they're doing work. This is right down to an early scene where he sees his men's terrorist videos, where Ahmed reacts again less as a man looking at horrifying propaganda, but rather a front man being very disappointed in his band members' music videos.
Now in proper Moe Howard form Ahmed, though the most intelligent of the men, is also a bit of an idiot he's just better at hiding it from himself. This is right down to their motivation where they are group yet couldn't be more westernized themselves. This is actually especially true to Ahmed's portrayal of Omar, which is again never exactly true to his intention. Again what makes this work in a comedic sense is that Ahmed stays pure to this throughout the film, and plays it as being perhaps somewhat oblivious to this contradiction. In turn Ahmed is consistently funny in portraying just how comfortable technically Omar in this such as his full embracing of a jogging neighbor while he and the men are transferring their explosions. Ahmed carefully shows not a hint of actually hating anyone, other than his own men, which I feel is key to making the film's tone work. The whole time Ahmed portrays this as less something he truly deeply believes in a dogmatic sense, but rather because it is something that has been decided for him. Even when he announces his intention to go about suicide bombing to his wife, Ahmed delivers his veiled statement as though he's decided to finally go on vacation or something.
A pivotal element in Ahmed's performance actually though is that he doesn't wink at any point and stays true to his character of Omar, which makes both the character and the tone of the film cohesive. This is as Ahmed portrays Omar most at ease at essentially not be a fundamentalist terrorist or even a fundamentalist in any way. This is particularly important to the few scenes Ahmed shares with a more religiously observant Muslim, who is not a potential terrorist, where Ahmed brings such a petulance in his treatment of the man. Again this should almost seem nonsensical however Ahmed makes it entertaining yet somehow natural to the character, and his skewed views towards his own religion. In every moment where he's actually trying to be terrorist Ahmed's great by showing Omar frankly at his most idiotic, such as his classical prat fall when firing a bazooka, or the whole final sequence where the men go to blow themselves up wearing ridiculous costumes. Ahmed makes for the right type of physical embodiment of awkwardness, however he goes even further to slowly throughout the sequence portraying the realization in Omar over his mistake. He ends up creating a bridge the film to a more dramatic intention as he attempts to talk Waj out of it. Ahmed manages to make this transition work, without somehow going too heavy, despite the film ending the way it does. Ahmed's performance, much like the film, is this incredible balancing act that manages to be quite entertaining while somehow making light of the dark material, yet somehow also create some depth to it. It shouldn't work, but it does, and Riz Ahmed's astute performance is one of the greatest contributions in making it so.