Here's my Pangolin Viral (Amplified damage to health) Build for corrupted, corpus and sometimes used on Grineer too.

A reminder:
Usually I would recommend to use Slash on Infested with Gas and/or Corrosive but Viral can do the job for other factions.

Viral on Corrupted:
+75% / Cloned
+50% / Flesh
Neutral on Ferrite/Alloy/Shield/Proto/Robotic/Fossil

Viral on Corpus:
+50% / Flesh
Neutral on Shield/P. Shield/Robotic

Viral on Grineer:
+75% / C. Flesh
Neutral on Ferrite/Alloy
–25% / Machinery

Viral on Infested:
-50% / Infested
Neutral on I. Flesh/Fossilized/I. Sinew