As the title suggests, this is my attempt to link Savitar's backstory and several things we have seen of him to another character, Eddie Thawne, due to Eddie more or less serving the comic's version of Eobard Thawne's ancestor's place.
Granted these reasonings are fairly contrived for a few of them, but bear with me.
Anywho, let's begin. (Kir if you just comment "This isn't what a theory is" I'll link you to Webster)
The What If
In the Season 1 finale, Eddie Thawne seemingly committed suicide to stop Eobard Thawne from killing Barry, erasing his great-great-great-great-great grandson from existence.
We later see Eddie's body and some of that cobalt material used by the time-sphere get sucked into the Paradox-Black Hole that Barry just left, potentially getting thrown into the Speed Force.
This possibility is what I'm latching onto for... literally everything that comes later.
What if Eddie was still just barely alive when he was sucked up into the Speed Force-linked Black Hole?
This massive alteration to his life would easily cause Eobard's existence to be threatened like we saw, such a derailment of Eobard's family history (Eddie never having a kid in the first place) would certainly erase him.
Now, here's where I draw stuff from the comics.
Comic Version of Eobard's ancestor, Malcolm
In the comics there is a character named Malcolm Thawne, not only is this guy the ancestor of Eobard Thawne and Bart Allen (Bart's actually half Thawne and half Allen from the 31st Century but is only Barry's grandson it's complicated)
He is Barry Allen's long-lost twin (the doctor who delivered them was drunk and caused the Thawne family to lose their child and said "I'll just give them one of the Allen twins, that'll fix it, hope he got thrown in prison forever) and grew up with the Thawnes, who were a bunch of thieves or something.
The thing that actually matters is the family jewel they had, it supposedly contained a great power that they used to commit their robberies (or something) and Malcolm found it in his possession.
He later discovered he was Barry's twin and got jealous over the good life he had (compared to Malcolm anyways, apparently the Thawnes were abusive) and used the Gem to gain power (I think it worked on jealousy and hatred or something)
Using the gem he could absorb the power of speedsters and use it for a variety of effects.
This is the first thing that makes me think Savitar might be Arrowverse Cobalt Blue and Eddie Thawne.
They both have a magic rock that grants them their powers and are both Eobard Thawne's ancestor (Eddie just went so far off track it was no longer a possiblity)
Savitar claims Barry made him who he is (I think)
Again, one of the clues we got was Savitar saying that Barry created him somehow (I think)
You could look at this a few ways I'm sure, but here's one.
Barry's weakness made Eddie shoot himself, and then get sucked up into the speed force.
If Eddie somehow managed to survive that experience, and found a way to connect himself to the Speed Force or was sent to the past to find that magic rock, he would've been created by the Flash.
"You made me who I am," By being too weak to defeat Eobard Thawne and causing a chain of events that made Eddie gain the powers of a Speedster.
Savitar said "I've been with you since the beginning"
This line had klaxon sirens going off in my head.
Savitar is someone we know.
There are a few candidates for this link we can say most likely cannot be Savitar and were with him "From the beginning"
Eobard: He was described by Abra as "not breaking you like Savitar did"
Vibe: Not even gonna explain it.
Joe: HE WOULD NOT KILL HIS OWN DAUGHTER
Henry: His last words were about how he "Was so proud of you" when talking to Barry, he would never intentionally hurt his son no matter what.
But there is another person who has been with Barry since the beginning in one way or another.
In season 1 we are introduced to Eddie as the "Arrogant Cop" who keeps a record of all his arrests and one ups Barry in the pilot episode.
Granted, Eddie wasn't as bad as advertised, he was actually a guy who wanted justice and came from a background of "The people in my town hated my family after my Dad did some stuff."
But, Eddie was with Barry from the beginning, his co-worker in the CCPD, the guy who went after The Flash, the guy who later was let in on the secret, and finally, as a man who Flash had difficulty letting go of the guilt for not being able to save.
Ronnie also fits the guilt bill but wasn't with Barry since the beginning, he only knew about Ronnie later on.
"I've been with you since the beginning" Because I am Eddie Thawne, and I was with you ever since you first got your powers.
Savitar said "I'm sorry you have to die" to Iris
Eddie was also to be married to Iris West, he loved her plain and simple.
During one of the "Julian, we're gonna make you Savitar's human puppet" sessions, Savitar made a genuine apology to Iris, seemingly resigned to, if disliking, that she has to die for his revenge.
"I'm sorry you have to die," Savitar doesn't want to kill the woman he loved, but he has to in order to make Barry suffer.
There are some things I haven't accounted for of course, how Savitar is known by many speedsters across the Multiverse (or at least Jay Garrick)
Why Eddie hates Barry now (Could be he is jealous of Barry's life and how he sacrificed himself for it)
And I'm sure a bunch of other things that people in the comments could thankfully inform me of.
But with the minimal clues we've been given, to me, Eddie Thawne seems like the most likely candidate for Savitar's true identity after he went crazy in the Speed Force.
Huuuu... I spent way too long typing this out.
Savitar is Eddie cuz of possible emotional attachments and cryptic comments he's made, along with bits and pieces from Eddie's supposed death scene.