What are the highest skill checks required by different DLCs? It would really help me with character planning.

I've seen a few 100 Speech checks throughout most of the DLCs. Smattering of Science, Medicine, and Explosives checks as well.

Probably others, but I can't recall them off the top of my head :/

I've never seen a 100 speech check, highest speech checks to memory are 90 with Graham and Ulysses.

Highest skill check outside dialogue to memory is certiant hologram emitters in Dead Money requiring 100 Repair to disarm.

If you get the Indy Vegas dialogue with Ulysses there is a 100 speech check after a 90 speech check.

To smack the taste out of Ulysses' mouth, there's a 100 science or 100 repair check to disable his little helper machines.

There's a 100 speech check with Lanius at the end to avoid having to fight him where you convince him to leave the Mojave.

I've seen countless 100's the past week or so that I finished DM, LR, and OWB. There out there, mainly in science if you're looking for a specific skill.