La regaste

Telling someone they screwed up should be considered one of the basic communicative functions. Let's look at two informal ways to accomplish this.

La regaste

At the tame end of the spectrum we have the verb regar. Always include the direct object pronoun la. Don't ask why la and not lo. If you must, think of la as referring here to la situación or la cosa. Here are some examples:

• La neta, la regaste. = Seriously, you screwed up.
• Pero no, la tenías que regar But no, you had to screw it up (like you always do).
• Es que otra vez la regué. = What happened is that I screwed things up again.
• Creo que debemos darnos tiempo para no regarla. We should take our time (in this relationship) so that things work out well.
• Está a punto de regarla. He's about to make a big mistake (and ruin everything).
• ¿En qué la regaste? What did you screw up? A possible answer: — En muchas cosas.

You can modify regar with words like feo, gacho and cabrón/cañón:

• De plano la regó bien gacho en casarse con ella. He should never have married her, big mistake.
• Ya sé que la regué cañón. I really screwed things up this time, I know.

Regar, literally water/irrigate, is also heard in relation to gossip: regar todo el chisme, spread the gossip.

La cagaste

To up the level of vulgarity, use cagar = take a shit. Note that la is still needed.

• La cagué. I fucked up.
• Aceptamos que la cagamos. We admit that we fucked up.
• Apple la cagó feo. Apple should never have released that update. It doesn't work.