Deadpool (Wade Wilson) and Black Widow (Natasha Romanova) are technically powerless but undeniably powerful Marvel characters who are anything but weak. The characters seem are evenly matched in a fight against one another, between Deadpool and the Black Widow's weapon arsenal and the fighting skills that they possess.
However, they have weaknesses that might give one or the other an edge. So, how would the Black Widow, the highly intelligent tactician and spy, do against the skilled merc with a mouth in a fight?
10 DEADPOOL WINS: BLACK WIDOW'S ATTACHMENTS
Black Widow formed a strong bond with her S.H.I.E.L.D team member, and the person who brought her in, Hawkeye, despite initially being a lethal spy. Whether out of true love on her end, obligation, or respect, it is clear that Black Widow has attachments and acts in defense of other people. So, if Deadpool lured Black Widow by attacking Hawkeye (or anyone else she acts on behalf of), into more danger than they could handle, it's entirely possible that Black Widow would swoop in (and risk herself in the process).
9 BLACK WIDOW WINS: DEADPOOL IS EASILY DISTRACTED
Natasha Romanova is a Red Room (Soviet training facility) trained spy, snipper, and killer. On the other hand, Deadpool is distracted by beautiful things and people (including women).
Black Widow's could reel him by distracting him with her beauty and then finishing the job in a fight. Deadpool tends to lead with his own version of charm, flirting and often being distracted by people and things that catch his attention. This is basically the thing that would be his downfall in a fight against Black Widow.
8 DEADPOOL WINS: HE'S BUILT TO FIGHT
Deadpool was literally built to fight, and that is seen in how he breezes through fights against multiple opponents. On the other hand, Black Widow was trained to do what she does (rather than be born for and with that fighting ability). There is something to be said about being born for something versus being trained to do jobs. There is such an ease to how Deadpool fights (even in high-stakes situations) that it almost makes fans question how important the fight actually is as he breezes through them all like a walk in the park.
7 BLACK WIDOW WINS: BLACK WIDOW COULD ATTACK HIS MIND
When fans consider that Deadpool's healing factor is slowed down if his brain is not 100% (not just mentally but also the health of his brain) then it's a matter of attacking Deadpool's mind (through psychological manipulation, which Black Widow can do) or even shooting him in the brain (which, for some reason in the comics nobody seems to do).
Black Widow could make seriously quick work of Deadpool if she did either of these things. She may not kill him outright if she did this, since he is a being with a powerful healing factor, but she could seriously disable him for a long while.
6 DEADPOOL WINS: HER WEAPONS COULD BE HER CRUTCH
Although Black Widow has an incredible arsenal of weapons, strong combat and martial arts skills, and intensive training, her weapons are her strength in a lot of ways, and that's a weakness. Her widow's bite, her guns, and all the weapons in her arsenal didn't stop Hawkeye from killing her in Ultimate Marvel. So, in a moment of weakness, as Deadpool does sometimes strike with bombs from a far when his target thinks it's safe (such as the start of his fight against Carnage), then she would be unable to fight back.
5 BLACK WIDOW WINS: DEADPOOL'S WEAKNESS FOR FOOD
In Night of the Living Deadpool, Deadpool is eating at a Mexican restaurant, and he eats so much that he slips into a food-coma. When he wakes up, he is surrounded by zombies. As tough as Deadpool seems, he has his moments where he shows carelessness, and Deadpool's food weakness is an issue that could ruin him in a fight against Black Widow, Black Widow could easily set some kind of a food trap, complete with pancakes, tacos, and chimichangas, and strike when Deadpool is about to pass out.
4 DEADPOOL WINS: BLACK WIDOW CAN BE KILLED
Although Natasha Romanova's Black Widow had healing power, anti-aging and disease resistance, and all kinds of gadgets and weapons, she was still killed off by Captain Americas (who broke her neck in the Secret Empire storyline). The fact that Captain America was able to this, shows that she can be decisively defeated in a fight, and Deadpool would only need to go for the jugular in a fight to finish it.
3 BLACK WIDOW WINS: DEADPOOL'S MENTAL STATE IS TOUCH AND GO
It's no secret that Deadpool lives with active mental health disorders, from ADHD to depression and schizophrenia. He experiences audio and visual hallucinations and experiences memory retention issues. Of course, his somewhat violent tendencies works to his advantage in a fight, but the instability of his mental health would certainly leave Deadpool vulnerable to Black Widow, a formidable foe who has a lot of control over her mind and her actions. A bad mental health day would be all she would need to exploit his disability.
2 DEADPOOL WINS: BLACK WIDOW'S MEMORY IS CHECKERED
Black Widow's mind suppresses parts of her memory, and that makes it impossible for her to remember the exact events of a previous fight. Although some might say that this is convenient (in that she could do a second fight against a previous foe without any fear, it is actually a glitch that would give Deadpool an edge. If Deadpool were to fight Black Widow, he would remember all of her tricks. So unless she manages to come up with new ones, she would forget fight details - perhaps, critical details, and he would remember everything.
1 BLACK WIDOW WINS: DEADPOOL'S VULNERABLE TO TRANQUILLIZERS
Although Deadpool is extremely resistant to many toxins and drugs, and even though he has a quickened healing factor, some drugs can impact his wellness - particularly tranquillizers. If enough tranquillizers get into his system, it can impact his strength and his fighting ability. Also, laser's are an issue, and when they're channeled to the right spot (such as his eye) it can take a long time to properly heal. On the other hand, Black Widow has a biotechnology augmentation that has made her body resistant to disease, and there is no mention of tranquillizers being able to weaken her. So, in this case, Black Widow would only need to grab a tranquillizer gun, load it up to the highest dosage, and attack Deadpool with it.