- And got the T-shirt
When you've got a day to give to it, try the introductions again. When you're ready to put them in the cage, give them a buddy bath -- the shared terror may help them tolerate each other a little. You can also try putting a tiny, tiny drop of vanilla just above the nose. That way, they'll both smell the same, and it may dampen their territorial tendencies a little.
Take any hideys out that only have one door. Hang some fleece forests so they're not always in each other's line of sight. Put at least two piles of hay in the cage, as well as two water bottles and feeding/pellet dishes. Separate those things so they can use them without getting in each other's way.
Other than that, just be patient. Usually a boar pair will work, but it may take a while for them to settle down.
How old are they?
Make sure you re-clean the C&C cage to get rid of all their scents, especially if one boar is getting to live in it while they are separated. If you must do that, let it be the smaller boar that usually gets picked on. But it would be better if neither boar has it all to himself until they are both in it. And then it should smell neutral when they are placed in it together after proper introductions have been completed as per the link.
After they are about 18 months old they should settle down quite a bit. Right now their hormones are raging. Think back to your teen years. . . .
(I should clarify that guinea pigs can reproduce before they hit the "teen years" so maybe I shouldn't call it going through puberty, but the overall bratty, obnoxious, irritable - "go away you are ruining my life!" attitude of typical human teens is what the pigs go through between about 6 to 18 months of age.)