The best replacement for struggle is challenge.

The best alternatives to struggle are rated as following:
★★★★★  challenge
★★★★  accomplishment
★★  labyrinth
★★  1960
★★  1989
★  peaceful
★  war of the ring
★  struggles

Your alternative for struggle is not listed? Suggest!
Speaking about struggle, one probably shouldn't forget about progress.

Other search terms related to struggle and their ratings are:
★★★★★ progress
★ class
You have in mind a companion for struggle and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of struggle in all years. Click on graph for more.
struggle
challenge
accomplishment