Learn Spanish (Latin America): No quería que los criaras sin disciplina. - I didn't want you to raise them without discipline.

The main verb No quería (I didn't want) expresses a desire in the past. When you express a past desire, influence, or emotion that affects what someone else does, the verb in the second clause (after que) must be in the past (imperfect) subjunctive.

How do I form the imperfect subjunctive criaras from the verb criar?

To form the imperfect subjunctive, you always start with the third-person plural (ellos/ellas) form of the preterite tense. For criar (to raise), that form is criaron. Drop the -ron ending and add the past subjunctive endings. For tú, the ending is -ras, giving us criaras.

Could I attach los to the end of the verb, making it criaraslos?

No, you can't attach it here. Because criaras is a conjugated verb, the direct object pronoun los (them) must go immediately before it. You can only attach pronouns to the end of infinitives, gerunds (the -ndo forms), and affirmative commands.

Since quería can mean 'I wanted' or 'he/she wanted', how do we know who the subject is?