Interest is the whole story
A card's headline rate is quoted per year but charged per day on the balance you carry. That single mechanic explains why a balance grows faster than the percentage feels like it should.
Everything else — rewards, fees, promotional offers — is secondary to whether you carry a balance.
Rewards versus debt
Rewards pay a small percentage on spending. Interest charges a large percentage on debt. If you carry a balance, the interest almost always wins.
The pages below show the arithmetic rather than asserting the conclusion, because the comparison is the useful part.
Repairing credit
Payment history and time are the two inputs you cannot shortcut. Secured cards, utilisation management and disputing genuine errors are what you can do in the meantime.
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All guides in this cluster
What an APR actually charges youRead the guideGrace periods and when interest startsRead the guideUtilisation: the ratio that moves your scoreRead the guideSecured cards: rebuilding with a depositRead the guideRebuilding credit after it goes wrongRead the guideDo rewards beat the interest you pay?Read the guideBalance transfers: the fee against the savingRead the guideFirst cards: what to look for at the startRead the guideBusiness cards and where personal liability sitsRead the guide