くせ

くせに

Even though…(Disdain)
Noun + のくせに
Plain Verb/い Adjective + くせに
な Adjective + なくせに

Meaning wise, くせに is a stronger version of のに. It expresses disdain, judgment, contempt, or criticism against someone. You shouldn’t use this until you get really confident in Japanese.
This pattern feels like “Even though you’re just a…” but only in nuance (as “just” doesn’t work in a lot of cases)

Note: くせに becomes a subject like が see example 2 in nouns.

Examples

Nouns

Tends to be “Despite” or “Even though“.

• 大人のくせに、子供を泣かせた
  Even though you’re an adult, you made a kid cry?
  
  
• 子供のくせに親の文句をいうな。
  You’re just a kid, don’t complain about your parents. 
  
  
• 警備員のくせに逃げた
  Despite being security, they ran away.
  
  
• 先生のくせに知らないみたいだ
  Looks like even though he’s a teacher he doesn’t know. (Really rude)
  
  

Adjectives

Functions basically the same as nouns.

• 避難されるに弱いくせに、よく人を非難する
  Despite him being weak to criticism, he often criticizes others.
  
  
• 頑張らないくせに、部下にもっと頑張るんだと言っている.
  Despite the fact he doesn’t work hard, he tells his subordinates to work more.
  
  
• 弱いくせによく吠える
  He barks a lot even though he’s weak.
  
  

Verbs

くせに typically translates as “Despite the fact” or “You did X so don’t...”

• 食べたくせに嘘をつくな
  You ate it so don’t lie. (Well YOU ate it so don’t lie, what the heck). 
  
  
• 勉強しないくせに合格したんだ
  Despite the fact he didn’t study, he passed. (A bit angry about it).
  
  
• 何もしないくせに人に命令するな
  You don’t do anything so don’t order people around.
  
  
• よく遊ぶくせに働かない
  Despite playing a lot he doesn’t work. 
  
  

くせ

Habit

Completely unrelated to the meanings above, くせ has another meaning of “habit”.
I’m listing it here mainly to preempt some confusion.

Examples

• 先生は質問に答えないという悪いくせがある。
  The teacher has the bad habit of not looking at raised hands.
  
  
• 指を鳴らすくせがある。
  (Someone) has a habit of snapping their fingers.
  
  
• 物を忘れるくせがある
  A habit of forgetting stuff.