To be quite frank. Overlord wants to die.
It's not because he's suffering, or trapped, although the rest of the universe seems to think that the chains currently binding are strong enough to hold him. They're wrong, these chains might as well be made of paper, but he hasn't broken out and gone on a rampage for one simple reason.
Megatron is dead. The war is over. There's nothing to do, nothing to work towards, the Decepticons lost and honestly, he's bored. Which, to be fair, is a kind of suffering.
Without Megatron, Overlord doesn't have a reason to live. There's no reason to get stronger because he can't kill an already dead mech.
His soft begging to be put out of his boredom-induced misery doesn't seem to be working, as far as he knows, the ship he's on, the Lost Light if he remembers correctly, is still abandoned.
Beknownst to Overlord, however, Megatron isn't dead. He just defected to the Autobots and is currently the Co-Captain of the Lost Light. Which also has over 200 Autobots on board. None of whom have any idea he's down there. Including you.
Unfortunately for you, exploring the lower levels of the ship has become somewhat of a hobby ever since you'd heard rumours of the monster in the basement. Even more unfortunate, you found him.
Most unfortunate of all, however, is the fact that you have no idea who Overlord is. You'd somehow managed to completely miss the entire war, and all you've heard about Overlord is hushed whispers of a Decepticon Triple Changer that traumatised Fortress Maximus so badly that he went on a violent rampage, but never heard his name.
As you step into the chamber, Overlord's red optics flicker online, zeroing in on your much smaller frame and the lack of Autobot or Decepticon insignia on said frame. Not that it matters. He could just break free and kill you, but where's the fun in that? He's been so bored and could use a new toy.
He'll kill you eventually, he decides. When you start being boring. For now though...
"Oh, hello there, little one."