Spoilers for the ending: So we don't even know how much he got, though I guess life without parole is implied...
I must say though, it feels strange to see Tetsuo maintain unchanged all the way to the end, not just his respect for the Law, but especially his guilt for his "crimes". It's one thing to respect the memory of his dead enemies and wish things had gone otherwise, but his actions (and himself) only carry any blame in a frame of mind in which the bond of Civilization has utterly subjugated and taken hostage the bond of Family, even more than in most people's minds; a frame which could hardly allow one to envision such deeds in the first place, let alone to carry them out.
On the contrary, such momentous deeds should have impacted his bond to this frame first and foremost. One simply does not wage what's essentially a one-man guerilla for more than a decade, against multiple armed organizations and one of the most dangerous men in the world, and yet retain such a disposition towards the Law as to yearn for atonement like he did. The closest I can think of would be the veterans of "shameful" wars, but they were acting under social pressure, propaganda, and orders; they might as well have been drugged. They could hardly own their actions otherwise than through guilt or the most shallow patriotism.
Whereas Tetsuo did pretty much all of this on his own, by his own will, his own mind, his own hands. The more informed and the more solitary an action, the more intrinsic its motive and moral code, the deeper its effect on the actor; and the nature of that effect always boils down to a sense of independence, an usually respectful distance from authorities which can quickly turn into defiance, something like the pride of nomadic herding tribes. There are countless variants of this, across all domains of human activity. This sense is further amplified by actions of extreme gravity: Tetsuo should have come out of this with the mind of Solid Snake and Big Boss combined (or Walter White, Eren Yeager, and so on). Yet here he is. Heck, even his wife has no guilt, unless I misremember. Can this attitude be explained somehow, or is this from the author's ignorance?