The archangel Gabriel is often described as standing at God's left side and, although he isn't flat-out evil, one of his main jobs was to help people die and transition to the afterlife. Thus, you may have heard Gabriel described as the "angel of death." But that isn't even the darkest thing that the left is associated with in the Bible.
According to Matthew 25:31-46, which describes a scene from Judgment Day, those who were to be saved and held in the grace of God (the "sheep") were separated from the "goats" and sent to the right. The "goats," those who were selfish and faithless in life, were sent to the left and condemned to the "eternal fire prepared for the devil and his angels." Ouch.
The idea that favoring the left meant moving away from God soon spread to other Western belief systems. Esoteric and occult traditions adopted the terms "right-hand path" and "left-hand path" to describe the two main (and opposing) approaches to magick. Those who take the left-hand path are believed to favor liberation, rebellion, and personal benefits over the greater good. In some circles, this choice reflects a desire to practice insidious, "black" magick, but, as time has gone on, that's come to be viewed as an oversimplification — if not flat-out wrong.
We'll admit that it's no picnic dealing with devices that were made with righties in mind (and it's still important to avoid eating with your left hand in India and other parts of the world). But, at the very least, being ideologically opposed to left-handedness seems to be a thing of the past. And if you take a close look at your thumbs-up emoji, things may start looking downright lefty positive.