I had a series of scenes in Hal 4 where a major character was a bit of a spare wheel. (Relax, no spoilers here.)
This character wanted to help during a major crisis, but nobody needed the character's assistance. So, the character went off and fiddled around for three chapters while the others got on with things. I wanted to make the character feel lonely, isolated, unwanted. Maybe I did, but it made for poor reading and no tension.
Why? Because when disaster hit and the others came to ask for help, the character had no real involvement. It's a bit like an emergency worker waiting for a call-out - they know all kinds of bad things are happening out there, but until they're personally involved it's just stories from the pages of a newspaper.
So, how to fix this? I'm rewriting so that this major character will be involved in the crisis from the very first minute. The character is going to direct the whole thing, ordering the others around and taking complete control over the situation. Then, when things go wrong, the character is right in the thick of it.
Aside from being in the midst of the interesting parts, I can also build the character's emotions up - joy at being needed, the pride of performing a job well, etc. That makes the fall much harder .. and good plots are all about hard falls, not moping around for chapters on end.
Simon Haynes is the author of the Hal Spacejock and Hal Junior series (Amazon / Smashwords / other formats)