In the Breaking Bad series, Walter White goes to Tuco's office to get revenge/deliver a message by causing an explosion. I could never understand: Did Tuco actually consider Walter White to be dangerous, or did he actually start to respect him enough to bring him into business?
I don't think that Tuco's response can be seen to be respect nor fear.
What Walt is (to Tuco) is uncertainty. Tuco is formidable, unpredictable, and savage. Those who know him are wary of him, even his own employees. Tuco rules because Tuco keeps all of his enemies (and potential enemies) on edge. Tuco, you see, can (generally speaking) predict all of his opponents moves. An embezzler or thief can't do their thing without Tuco sniffing it out... but the embezzler or thief cannot predict Tuco. He's "crazy".
It is almost certainly this way for everyone Tuco meets. Even before they've said a word to each other, Tuco will have the measure of the other person, but that other person will not have Tuco's measure.
Walter White may have been the first person that Tuco ever met where this wasn't true... Tuco isn't in the same circles as Walter. He's never met anyone like Walter before. Walter is impossible to predict. He isn't intimidated like the others. For Tuco (and, alas, for everyone else, including us viewers) it's very hard to figure out what makes Walter tick.
Tuco handles this fairly intelligently too (how awesome for us, the viewers!). In any other show, Tuco might have tried to escalate, only to be taken out by a car bomb or whatever. Instead, Tuco acts cautiously. He doesn't back down, but he doesn't lean in either. And as later episodes demonstrate, he calls to his superiors for instructions on how to handle such a novel situation. This is a sophisticated response, in my opinion.
After the number Walt pulled on him by blowing up half his building, Tuco knows for a fact that the man is dangerous. And maybe a little bit crazy also, because, after all, he entered Tuco's den alone and defeated everyone singlehandedly with just the help of a little chemistry.
I don't know if this action gained Tuco's respect or caused him to fear Walter (which I personally doubt), but it certainly caught his attention, which was what Walter was aiming for.
That stunt indicated that Walter meant serious business (both literally and metaphorically), that he could produce an outstanding product and that he wanted a partnership (a distributor) with Tuco. And that he was ready to do anything in order to achieve his goal.