How was Stalin undemocratic?

Hitler's government was undemocratic because when the president of Germany Hindenburg offered him the highest and powerful position Chancellorship as the first step he passed a decree known as the 'Fire Decree' he take away the freedom of speech,assembly and press through this act he was trying to threw away democracy from Germany and then he passed another act known as the 'Enabling act'. In this act he ordered his army troop to imprison all the parties except the Nazi party.