Woe, ‘owy,’ means lamentation, extreme sorrow.
Ill, ‘ra,’ means bad, adversity, calamity, loss, exceeding harm, disaster.
Isaiah is addressing the Israelites that have rejected God in the sense that they should have accepted God, but did not. This principle applies to all people throughout the world and throughout history.
Wicked people come in two categories.
First, there are those who reject the Savior, Jesus Christ, and thus are identified as unbelievers.
Second, there are those who have believed in the Savior, Jesus Christ, but choose to not pursue their spiritual life as God has defined the spiritual life. They live outside of Gods will, even though they are saved and destined for heaven. They are either indifferent toward God and doctrine, or they use their own invented and false spiritual life.
For the first group, unbelievers, the Lake of Fire is the result of their chosen lifestyle. For the second group, loss of reward is the result of their chosen lifestyle.
In life, the result of being saved, is infinitely greater than not being saved.
In the Christian life, receiving reward due to ones advancement to spiritual maturity is infinitely greater than receiving no reward due to not advancing to spiritual maturity.
So, in the previous verse, great is the reward and destiny of the mature believer.
In this verse, the loss of salvation or reward, is a tremendous loss. And woe and ill, are two words that describe the extreme degree of these losses.
The next life is an infinite life, one in which a person can define his own future, right now, if only you make the right choices now.
However, far too many people live their lives in rejection of the very things that are most important to them. They hate their life, they hate God, they hate Christ, they hate doctrine, they hate their spouse, they hate their children, they hate their job, they hate the circumstances of their day to day life, and so on, and so on.
Spending far too much time in rejection of the very things that God has provided in order to make your life better, to help you train for orientation to life, to help you prepare for that far better life which is ahead, and so people will miss out on the big picture because they choose to be angry with the little things and the important things that God has provided.
So, continue in your rejection of life and the many things that should be important to you, and you will end up in the ‘woe’ category of life, and be miserable because of your own doing.