Sari and the Key
Hey, I've been rewatching Transformers Animated recently and one thing that's bugging me is the lack of distinction on what the key can do and how it seems to react appropriately depending on the situation for plot convenience.
Ability 1: Fixing
Probably the most memorable. It was used three times in the series pilot Transform and Roll Out, fixing up Prowl, Bumblebee, and later bringing Optimus essentially back from the dead (with the help of the AllSpark itself).
This ability is used numerous times throughout the series, probably more than any other one of the key's ability. Given that it was empowered by the AllSpark, its no surprise the key is able to fix damage, whether it's mild or severe.
Ability 2: Upgrading
The second most used ability is probably upgrading man made machinery. Again, not bashing the idea of the key being able to do this since it was empowered by the AllSpark. Things that have been upgraded by the key range from Soundwave himself to Bulkhead's sculpture in Headmaster.
(Personally I wish there was more distinction to this, since Soundwave became self aware "due to the last surge from the key." I suppose it means there's a spectrum of autonomy for man made bots that the key can continue upgrading into self awareness, but I digress).
Ability 3: Overloading
Again, with the AllSpark having no limitations to it's power, it makes sense that the key might be able to overload technology. Examples include overloading Swindle's time device in SUV, and Transwarped part 3 when Sari overloaded her own circuitry.
Ability 4: Detecting AllSpark Fragments
This one is self explanatory. While it probably didn't need to exist since the bots are shown to be able to detect fragments due to their massive power signatures, it still feels reasonable. Although, occasionally, the writing flips the script and says the key can attract the fragments to an extent, if close enough (shown in Mission Accomplished).
Where it gets tricky:
With four abilities (and those are the main ones, there might be more) it can be tricky finding a way to distinguish how the key will react in certain situations. As far as I can tell, its reaction is based solely on plot convenience.
What bugs me is that it seems Sari (and indeed, anyone who uses the key, but since Sari is the keeper, mainly her) knows how to use it specifically to fix vs overload, etc.
I understand the writers had limitations but one of the reasons Sari might be classified as "over powered" by the fandom is simply because of the lack of distinctions to her (and her Key's) abilities.
(This is definitely open for discussion if anyone has anything to add!)