"I need you to be strong."

Translation: Potřebuji, abyste byl silný.

[JBHayven]

Could there be "mocný" instead of "silný"?

[endless_sleeper]

Not really.

Mocný is more like 'powerful, mighty, potent, influential'

[Jane308391]

Please, why is it 'abyste byl' and not 'abys byl'?

[BoneheadBass]

Translations using "abys byl" also are accepted.

[Chessnecof]

Why can we leave out the personal pronoun (?) tebe nebo vás?

[VladaFu]

It does not belong there at all.