In your opinion, who are the biggest victims of Power Creep in the entire series?

Be as thorough and brutal as necessary. No ninja is off limits, as well as no arc. It can be Part 1 only PC, Shippuden only PC, or a crossover, like one of my examples shown; it helps obviously to use canon material, as it is most reliable, and able to hold to account and reason, and generally stays consistent and measurable. Depending to what scale we're talking, a lot of ninja can qualify technically as Power Creep victims, as a lot of characters get power ups, and many get multiple on screen, and there are pivotal fights or defining moments that highlight when a character clears, plateaus, or jumps in scaling and becomes painfully evident. Also, there is a huge range in screentime that certain characters are allotted or granted, as usual due to significance in plot.Some are more inferred, and dont have an exact point you can pin down to say, "THAT'S when [-----] entered a new tier in power".

• My 2 examples, are Kakashi and Sasuke, both in Parts 1 and 2, if we're being honest, mainly in part because they have several fights across the series, so it's fairly easy to track and scale where they stand from fight to fight in the overall tiers of power at large. Zabuza to me is a very important rubric in scaling Kakashi as a Part 1 Ninja, in specific, mainly because it was one of the few fights even going back to Part 1 where he wasn't facing someone with a broken hax ability (see Itachi[Tsukuyomi, Ep 82]), that was hinted at seemingly being an elite jonin-level ninja for his respective Village potentially, and Kakashi made EASY work of him, not once, but TWICE. Had 3 very inexperienced Genin accompanying him, that had literally never been on a mission before as official ninja holding him down as potential hostages, and an actual hostage on top of that, and he was TOYING with Zabuza, literally trolling him with the Sharingan, copying his jutsu, adding insult to injury. However in Part 2, he had the help of Naruto and eventually Team Guy also, yet they still struggled with a solo Akatsuki member, one of the bottom 4 in strength or ranking, although still strong in his own respect, Deidara[as he captured Kazekage Gaara by himself]. And this is with Naruto getting amped by a 2-Tailed Cloak anger buff with Kurama's chakra seeping out, and with him[Kakashi] having considerably more stamina and dexterity with the Sharingan, training it to the point where he could use MS, multiple times in one fight [Kamui]. And Pain.... well, we remember how that fight went. Nagato is a pure unit, on a wildly different scale of power. Kakashi really had it rough in the pick of the draw for fights he had to engage in for Shippuden, considering how his reputation started, and we go from thinking he pretty much can't lose in Part 1 up until Itachi, to not seeing him be able to claim a win in Part 2... technically ever[unless I'm forgetting something]? Sasuke was a child prodigy, and ignore it if you want, but him curb stomping the Demon Brothers was his first "fight" if you want to call it that on screen, ignoring the preliminary bell test against Kakashi. He took care of them on his own, and had at this point, already impressed Kakashi by knowing the Fireball Jutsu as a Genin prior in the bell test, as most Genin dont even have a solid understanding let alone mastery of any level of elemental changes in chakra nature. He contributes in a solid fashion in his screen time against Zabuza in fight 1 alongside Naruto, and in fight 2 against Haku, he gains his first Sharingan buff. Gets mopped by Lee in their first encounter, however instantly copies his Taijutsu with the Sharingan, and matches his skill visibly in Taijutsu in under a month, while also adding Chidori to his arsenal when training with Kakashi in the Chunin exams arc, a staple jump in power we see from Sasuke in Part 1, the 2nd only after the Curse Mark. Itachi was always stronger than him, so him getting dogwalked by him in the presence of Naruto, Kisame, and Jiraiya doesn't exactly count as creep, I just added it for comedic purposes, partially. But Naruto learns the Summoning Jutsu from Jiraiya, as well as the Rasengan, and in their clash on the rooftop, it is clear who is in the lead, as him being the smarter, more skillful and equipped ninja for his age, compared to Naruto for the first time does not earn him prestige, and it became painfully obvious him and Naruto had switched places, as if it already couldn't be argued when Naruto summoned Gamabunta and defeated a full-power duo of Gaara and Shukaku. And this doesn't stop in Part 1 either with Naruto and Sasuke overall. For the entire duration of the series, Sasuke is engrossed in training and gaining power by whatever means necessary to surpass both Itachi AND Naruto in the beginning, and later just Naruto, after "defeating" Itachi in Shippuden. For the entire series at several notable points, even if not facing one another as combatants, they essentially take turns one-upping each other in power cliffing up until the until the very end of Shippuden.