Avoidable, unavoidable, evitable and inevitable

avoidable

adj    from avoid + -able  from es- "out" (see ex-) + vuidier "to be empty ‘clear out, get rid of’
​that can be prevented
Many deaths from heart disease are actually avoidable.

I don't reckon a steep learning curve is avoidable.
 

unavoidable

adj    from es- "out" (see ex-) + vuidier "to be empty ‘clear out, get rid of’
​impossible to avoid or prevent
unavoidable delays
Recession at the time seemed unavoidable.

From my point of view, a steep learning curve is unavoidable.

evitable

adj    /ˈɛvɪtəb(ə)l/  evitabilis ‘avoidable’ (from evitare ‘avoid’).
rare
Able to be avoided or prevented; avoidable.

The consequence may be evitable or inevitable, I'm going to do it anyway.

inevitable

adj 1     from in- ‘not’ + evitabilis ‘avoidable’ (from evitare ‘avoid’).
that you cannot avoid or prevent
SYNONYM unavoidable
It was an inevitable consequence of the decision.
 it is inevitable that It was inevitable that there would be job losses.
A rise in the interest rates seems inevitable.

Thanos was inevitable.

The underlying Windows installer technology caused us a steep learning curve, that's inevitable.