My level of disappointment and frustration is unspeakable. 2 big4s, 3 leading strategy houses, and 2 other top 25 consulting firms have dinged me in the final rounds. anyone with similar experience?

You can lessen those feelings by breaking down what went wrong at each one, see if there is a trend.

with every rejection you got more frustrated and anxious, maybe even scared. This may have showed in the last interviews you had. So it is difficult to work out a trend. The fact that you went to the last rounds means you are good material. Nevertheless, in the last round you would be usually meeting senior people. Think about this specifically.

I got rejected a couple of times in final rounds with partners. I was asked unusually tough technical questions and failed to answer them well enough.

It may not be anything to do with you at all. Firms will often decide not to hire but don’t always want to let on. Or the bar is raised so high it’s in practice the same thing. Or the firm is dysfunctional and without alignment all the way through as to what they are looking for (almost certain in the Big 4). In an uncertain market there’s a lot of smoke and mirrors about real hiring intentions and poor guys like you are the victims. So yes: think about the learning points but while your experience is certainly a little extreme it’s not completely out of the ordinary.

Either the OP has had extraordinarily bad luck (in coming across the scenarios Recruiter Too describes) in succession, or they are doing something which is sabotaging them. My instinct, given that there is a time investment to move someone to Partner round, that it is the latter.

I've had similar experience over the last few months, it's gets a little disheartening :(Always seems like it's going well then BAM you don't have xyz experience. Funny that, the CV says so, I said so in interviews 1 and 2 and yet you thought somehow I was going to magically get that experience?I think it's just basically someone else just has that biiiit more experience or they just didn't like me. Which is fine, I don't want to go big 4 I'd just me moving to the same place with a different name. My advice is try and get some other experience, get your feedback and then try tackling it from another angle. :)

there is difference between what interviewers tell you and what they really think. this can be illustrated through the following ground breaking mathematical formulaWhat you hear (A) = What they think (B) - Political Correctness (C)(C) is therefore the difference between (A) and (B)