14. You Can Use Grenades To Kill Vipers
Vipers are another common nuisance in XCOM 2, restricting the movement of your soldiers and causing significant amounts of damage over several turns, or just dragging soldiers away from the rest of your team. But, its actually possible to completely obliterate a Viper with just a single grenade, and if positioned just right, the explosion will do no damage to your own soldier.
Considering just how much of a pain these new additions can be in XCOM 2, and how often they can be the deciding factor in a tense situation, this is a pretty vital tip, and one the game leaves up to you to figure out.