Many of the characters in this work are obstacles to Christian's pilgrimage and hinder him in some way, either mentally or physically. You can tell how the characters in Pilgrim's Progress demonstrate the traits for which they are named by their names themselves. For example, Obstinate stubbornly tries to convince Christian to turn back. Pliable is easily manipulated into going with Christian at first, but he soon turns back when he sees it isn't going to be fun. Christian is discouraged by them.
Consider this next example:
"The man that met thee is one Worldly
Wiseman, and rightly is he so called: partly because he savoureth only the
doctrine of this world"
Look through the work, find the characters, analyze their names and you will see why they are named thusly and how they affect Christian's journey. Remember that in this allegory of the Christian life, humans enounter many obstacles on the path to eternal life.
One of the hardest evil persons for Christian to resist is Apollyon. His name is not as obvious as "Obstinate" or "Pliable" because it is a Biblical reference. Apollyon is one of the fallen angels in the Bible and many Bible scholars believe that he is the Antichrist. You can see, then, why Christian must struggle harder against him than the others. This struggle is a major delay.
There are some characters that have a positive effect on Christian. Goodwill, for example, encourages Christian on his journey:
"Good-will. Yes, there are many ways butt down upon this, and they are
crooked and wide: But thus thou mayest distinguish the right from the wrong,
the right only being straight and narrow."
Or, when Christian's burden is lifted towards the end of the work, Greatheart encourages him and explains:
The pardon that you and Mercy and these Boys have attained, was obtained by another, to wit, by him that let you in at the Gate;
and he hath obtain'd it in this double way, he has performed Righteousness to
cover you, and spilt Blood to wash you in."
This should get you started on finding other characters and examining how they affect Christian's journey.