Focus lens and warframe :: Warframe General Discussion
Anything that will kill a lot. Saryn, Ash, Ember, whatever. You may want to take "stealth" approach though and put lens into Ivara or Loki and go on stealth kill rampage for 500% bonus. P.S. I heard that "focus only from doing stuff with this thing" is actually a bug. So they'll fix it to work with shared affinity one day.