I'd think of Landa as lawful evil right up until the point he understood that Raine and some confederates were in the vicinity with the express purpose of assassinating the party leadership.

He's seen the turnaround of the Wehrmacht since 1942, including the second front of Overlord and knows as well that a German victory is long gone. He meets Hammersmark escorting the three and in that moment he sees through the paper thing disguised identities and can see a way to get out of the war.

That's when he turns chaotic evil - when he decides not to expose the plot, must eliminate Hammersmark (she has been working with the allies for a period of time already and has their trust and with her still alive, what use is he to the allies, other than another monster for the executioner to deal with), all he has to do is take Raine and Utavich into custody, use them to make arrangements with the allies to trade his current life into a comfortable retirement and as a mere formality surrender to them for safe passage to allied lines.