VET

I always thought of it like this:

He was an experienced IDPD officer during the times when his home world and, consequently, IDPD struggled with corruption. He participated in many missions fighting monsters form different worlds, but was never promoted despite showing his effectiveness (who knows, maybe his superiors were jealous of him or something). While not having a high rank he was still valued for his combat and engineering skills and assigned to a special strike unit where he had an opportunity to work with all kinds of different weapons.

The old uniform he is wearing and the equipment he used to have were in poor condition right from the start when he was issued with it due to organisation's poor "financial decisions".

One time during the mission he ended up being the only survivor. 

 

Back when VET was an officer IDPD units used special devices in order to communicate with HQ and trackers to show their coordinates and virtually nothing could be done to contact them otherwise. VET's communication devices broke and he was stuck unable to contact anyone. You might ask why didn't anyone send a rescue team. Well there might be several reasons:

1) Maybe the whole squad was immediately presumed dead.

2) Maybe the rescue operation would have been too dangerous and expensive and thus economically unfeasible.

3) Maybe the superiors didn't want to harm their reputation by showing their poor management skills in allowing this kind of situation.

Anyway, back to VET. Imagine being stuck in some hostile environment were everything is trying to kill you when you know for a fact who is responsible. Yea, being stuck like that for 40-something years made him become a lot more hostile and resentful.

Because of his bad equipment he had to rely on old weaponry scattered throughout the wasteland to survive. There were also periods when he didn't have any ammo or working weapon at hand and was forced to hide in ruins of ancient buildings, laboratories and etc.

At that time he used his engineering skills to create his weapons (the sword and deflector). While not made of the best materials they could still get the job done.

NUCLEAR THRONE:

VET doesn't know much about the Throne, besides that it's some kind of ancient teleportation device. He decides to find it out of not having (at least in his point of view) anything else to do and his mental state. After all this time he doesn't really care if he has to finish off a bunch of sentient beings that didn't really deserve it. Maybe he just wants to return home because he is tired or it's purely out of revenge he wants to enact.

ULTRA LORE:

ULTRA A is quite straightforward: found a purple crystal, managed to make it work as a power element and... BOOM! There you go. Cool purple sword that either has an unlimited power supply or just needs changing the crystal every now and then.

ULTRA B:

Who said that corruption just magically disappeared or that there will be no radical groups that decide to oppose the current regime or that they won't have access to portal technology? CORRECT! NOONE. These guys are ex IDPD soldiers, revolutionaries, some are in there for personal gain but one thing is certain: their leaders have decided that recruiting a violent mutated victim of the system would help in both military operations and further exposing the current regime, so they are willing to send reinforcement to help him on his way out.

There are two possibilities:

1) VET returns to his home world and helps the rebels with operations and pushing their agenda.

2) He continues looping and exposes how incompetent current IDPD forces are.

When encountering Lil Hunter there are several possibile scenarios:

1) VET believes IDPD want to finish him off and Hunter is with them.

2) VET understands that Hunter is in the similar situation but can't do anything about it since Hunter is already insane and hostile.