Grappled in 5e DND is a potentially lethal condition, in the right circumstances. It is otherwise not all that bad. There are plenty of counters available.
Frightened in 5e is a somewhat annoying condition to deal with, specifically for melee users. Luckily, there are quite a few counters for it.
Exhaustion in 5e is one of the most brutal conditions that are possible. It is a condition that can directly kill your character.
Deafened in 5e is one of the least severe conditions, depending on your circumstances. In fact, it is also a buff in some situations.
Charmed is a 5th Edition Condition that is usually pretty tame. However, it can quickly become serious in certain situations.
Blindness is a condition in 5E DND that removes sight of an affected creature. In some cases, it is a very difficult condition to deal with, but not usually.