The best replacement for reactive is proactive.

The best alternatives to reactive are rated as following:
★★★★★  proactive
★★  proactive policing
★★  responsive
★★  neoplastic
★  proactive management
★  proactive approach
★  inert
★  acute schizophrenia
★  reactive
★  septic arthritis
★  original slingshot
  event driven
  non reactive
  reactionary
  nonreactive
  particle
  deliberative
  proactive marketing
  proactive definition
  pearl reactive
  unreactive
  process schizophrenia
  proactive quotes

Your alternative for reactive is not listed? Suggest!
Speaking about reactive, one probably shouldn't forget about alkali and alkaline earth metals.

Other search terms related to reactive and their ratings are:
★★★★★ alkali and alkaline earth metals
You have in mind a companion for reactive and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of reactive in all years. Click on graph for more.
reactive
proactive
proactive policing