Regardless of whether or not Loki is actually evil, he is certainly a jerk. On one occasion, Aegir had all of the gods over to his house for a party. They were sitting dowm, talking peacefully, when Loki began to seethe over compliments being given to the diligence of Aegir's servants. Loki grabbed his dagger and killed the servant Fimafeng and ran off. Naturally, there was quite an uproar over this event. Loki wisely decided to make himself scarce.

Loki returned later and demanded a cup of ale. None of the gods wanted to have anything to do with Loki, but he reminded Odin that he had once promised not to drink unless Loki had been offered a drink as well. To avoid a conflict, Vidar stood up and gave Loki his sit and a cup of ale.

After Bragi told Loki that he would pay him well if he did not cause any problems, Loki began to insult the gods and goddesses one by one. He called Bragi a bragger and a coward. Then he called Bragi's wife, Idun a wanton woman. He then told the crowd that the goddess Gefion had slept with a man because of the necklace he gave her. He then proceded to call Frigg a whore, and from this point on, he becomes truly vicious.

He told Freya that she had slept with every man in the room, and that once she slept with her own brother. He went on to say that when the gods found them in bed, she farted.

He told Njord that once Hymir's daughters straddled his head and pissed straight into his mouth.

The insults continued until Thor waltzed in with his trusty hammer Mjollnir. Loki was smart enough to fear Thor, and told Thor that he respected him enough not to insult him. Then Loki turned around and left the party.

Source: The Norse Myths by Kevin Crossley-Holland pages 162-168