If a character really needs or wants to succeed in some action, you can let them have a bonus in exchange for some trade-off penalty in something else that potentially has a side effect on the action being attempted. For example, a character might be able to jump a greater distance than normal, in exchange for some Fatigue points or a chance of pulling a muscle. Maybe they can pick a lock faster than normal, in order to evade a palace guard without being seen, but if the roll fails they drop their lockpicks noisily.

Some trade-offs like this are built into some rule systems, especially for combat manoeuvres such as All-Out Attack or All-Out Defence, but you can go a long way adapting a system to increase flexibility by inventing new trade-offs that characters might want to make. There's no need to to spell them all out beforehand either - a good GM can concoct such things on the fly when a player expresses a desire to concentrate extra hard or put extra effort into doing something critical.

Transcript

GM: Annie, your berserk rage trades off accuracy for power. Roll.
Darth Vader: 10.
[SFX]: Throw!
Luke: Missed me!
Darth Vader: I didn't need to hit.
[SFX]: SMASH!
GM: Corey, Dex roll.
Luke: 7.
[SFX]: whooosh! {Luke is sucked out}
R2-D2: Wait wait wait... So it's a vacuum in there?
Han: {not dead yet} It'll be the Bernoulli effect. Probably a power generating wind turbine column using the temperature differential between the base and the top of Cloud City.
{beat}
GM: Yes. Yes, that's it.