Maybe Abbadon is a spy for Ben. He is someone with connections off the island. He is also close enough to Widmore to get useful information. How else would he know about Locke unless someone who has seen or been to the future.

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When will I learn? The answer to life's problems aren't at the bottom of a bottle, they're on TV!

Abbadon was not the orderly that was present when Locke first woke up in the hospital after falling down.

As for whether Abbadon's good or bad- he might have switched sides at some point. (In earlier episodes he seemed to be working for Widmore and in the last one, for the island)

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"Bear...? Is that you?"-- Hurley S03E4

Twins maybe?

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" We kinda like knew that forever ago." -Hurley SE4EP8

Abaddon is an absolute, complete, total, whole mystery to me. I do NOT know what to make of him. He has me baffled.

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`Dear, dear! How queer everything is to-day! And yesterday things went on just as usual. I wonder if I've been changed in the night? Let me think: was I the same when I got up this morning? I almost think I can remember feeling a little different. But if I'm not the same, the next question is, Who in the world am I? Ah, that's the great puzzle!'

-- Alice, from “Alice’s Adventure’s in Wonderland”

Abadon is an agent for Widmore the same way Alpert is/was an agent for Ben. I also don't think Ben has given up anything to Locke. He may have said that outside the cabin, but Ben is Ben and he hasn't yielded anything. My guess is that he is stepping down on a temporary basis so he can get revenge on Widmore for the death of Alex. That is his primary agenda at this point, everything else will lead to that goal and him landing in Tunisia in a winter parka (by the way, I think he has it on not because it was cold where he came from but because he wasn't sure where he would land). Somehow they knew to look for Locke when he was a child and Alpert found him first. Widmore didn't know who Locke was until much later, and then only because he fell from a building and didn't die (I think that's what caught their attention, and his survival against all odds as a premie caught Alperts attention, or at least built a case for him being the chosen one). Which leads back to Widmore and his search for the island....the Losties that get off the island are, in my opinion, the key for anyone who wants to find the island again (Ben or Widmore). Widmore will want them to go back to the island because the island wants them back and he can follow them there. Ben won't want them to go back until he has his revenge for Alex, at which point he can go back and take over again.

I like this line of thought.

Ben can't possibly have thought for a second that his days are over and Locke's are starting. It's a shift of roles and one much desired by Ben especially after Alex's death.

I also like the connection you suggest between Alpert- Widmore and the tragic events in Locke's life.

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"Bear...? Is that you?"-- Hurley S03E4

If Abaddon/Alpert/Widmore are altogether could it had been when Alpert did the test to see if Locke was their way to getting the island back Alpert didn't think Locke was the "chosen one" then when Abaddon visit John knowing somehow he'd wind up on the island and would be the key to getting the island back. To me that's putting too many together. What if it's Widmore and Alpert are both trying to get the island for themselves trying to outwit each other in doing so, and Abaddon is working both sides because he wants the island to himself.
Was it ever reveal who was the leader before Ben took over, could it had been Abaddon and Ben pulled some kind of stunt like "move the island" and proclaim himself to be the leader. We hadn't seen if Alpert, Abaddon or Widmore had been on the island. I'm not completely sure that who Locke see was the same Richard as we seen when he was given something that told him the man who con Locke was on the island maybe that's why Locke didn't reconize him. You could see when the teacher was telling the teen Locke about Alpert from Portland he knew the name, unless Locke can remember names but not faces.
My head hurts too much from thinking about these things haha.

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Standing in the ocean with the sun burning low in the west
Like a fire in the cavernous darkness at the heart of the beast
With my beliefs and possessions, stopped at the frontier in my chest
At the edge of my country, my back to the sea, looking east

Abbadon wanted Ben to go on a walkabout.

I wonder if the moment Locke left to go Australia, if that is when Ben found out about the tumor. The island was giving Ben a sign that his time was up, but not a sign that couldnt be fixed since Ben still had to guide Locke.

Cool idea. Ben found out about his tumor 2 days before the plane crashed, but I'm sure he was feeling the symptoms when Locke went to Australia.

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" We kinda like knew that forever ago." -Hurley SE4EP8

I agree with this statement.

I think Richard's disappointment in the young Locke's choice of the knife did not make him discount Locke's "specialness" to the island but rather made him think maybe he was meant for the other side (Widmore/Abbadon). That's why he was so pissed.

Is the possibility of Ben and Locke being brothers being pursued anywhere? I missed the first couple minutes Thursday but couldn't Locke's birth mother have been the same woman as Ben's mother, chronologically I mean?