Inflation means price rise. When price rises, goods & services becomes unaffordable to the poor , salaried & middle class, so it is unjust.
On the other hand inflation is beneficial to the investors, producers creditors etc. As prices are rising, investors motivate to invest more, so production, income & employment increases. Whereas deflation is worst as it slows the whole economy. Prices are falling , so people were not ready to invest, production & income decreases & people are retrenched, so unemplymentincreases. So deflation is worst.