Confusingly Big Heart

For all of his bountiful trust issues, Tyson is far too forgiving.

It’s summed up perfectly in this thread with flight-of-the-thieving-magpie:

What Jim finds more shocking than any of the rest of it - even the dent - is that having been bitten so badly so many times by dogs, Tyson is still so fond of them. Jim would not be nearly so tolerant. It says a lot about Tyson’s character, that he is willing to look past so much, to press on with his life and to continue facing things that by all rights should scare him or at least make him horridly uncomfortable. To have fondness for something, or someone, who has hurt him so badly is a clear sign to Jim that this man is either extremely stupid or has a confusingly big heart and a kind disposition that cannot be changed so easily. Already, Jim knows that he is not stupid.

It’s no wonder he’s been taken advantage of so easily.

And here with blackvclvct:

He’d been burned again and again. And yet, Tyson still offered out his heart and compassion - his body and soul, for friendship and love, and even that old lady down the road with a barbed tongue and far too many shopping bags - not without caution, but aboneheaded determination to give until his confusingly big heart had nothing left to offer. 

No matter what harm The Colonel does to him, Tyson will still come when he calls and will always love Sebastian Moran. No matter how much he despises the work he does for the Moriarty Mirrors, Tyson will jump through a thousand immoral hoops to please them. He is loyal to a fault.

Tyson isn’t dumb. He had always has an escape plan and a backup plan for every backup plan. He weights every risk against the reward, but Tyson has an odd reasoning for which risks are worthwhile and even if he’s bitten every time, Tyson will continue to offer his hand if there is even the slimmest chance of him helping someone else.

Once bitten, twice shy - yes, that is a core component of Tyson’s character. But Tyson still has to try. It’s compulsive. He can’t leave a friend behind. He can’t leave a good deed undone. With more caution, bandages and an escape route on hand, but Tyson will still put his hand out.