As adjectives the difference between unhandy and difficult

is that unhandy is not handy, unapt, clumsy, not dexterous while difficult is hard, not easy, requiring much effort.

As a verb difficult is

to make difficult; to impede; to perplex.

Concentrate is a synonym of thicken.

As verbs the difference between concentrate and thicken

is that concentrate is while thicken is to make thicker (in the sense of wider).

As adjectives the difference between dark and ominous

is that dark is having an absolute or (more often) relative lack of light while ominous is of or pertaining to an omen or to omens; being or exhibiting an omen; significant.

As a noun dark

is a complete or (more often) partial absence of light.

Mettle is a related term of bravado.

As nouns the difference between mettle and bravado

is that mettle is a quality of endurance and courage while bravado is a swaggering show of defiance or courage.

Composedly is a related term of peacefully.

As adverbs the difference between composedly and peacefully

is that composedly is in a composed manner while peacefully is in a peaceful manner.

As nouns the difference between courage and firmness

is that courage is the quality of a confident character not to be afraid or intimidated easily but without being incautious or inconsiderate while firmness is the state of being firm; strength; permanence; stability; hardness; resolution.

As a verb courage

is to encourage.

Unfruitful is a related term of dull.

As adjectives the difference between unfruitful and dull

is that unfruitful is of or pertaining to not bearing fruit (usually figuratively) while dull is lacking the ability to cut easily; not sharp.

As a verb dull is

to render dull; to remove or blunt an edge or something that was sharp.

In obsolete terms the difference between cause and force

is that cause is any subject of discussion or debate; a matter; an affair while force is to allow the force of; to value; to care for.

As nouns the difference between cause and force

is that cause is the source of, or reason for, an event or action; that which produces or effects a result while force is strength or energy of body or mind; active power; vigour; might; capacity of exercising an influence or producing an effect.

As verbs the difference between cause and force

is that cause is to set off an event or action while force is to violate (a woman); to rape.

As a proper noun Force is

falls. used in place names.