Sugar

Source: YT Sarah Hallberg.

Non-necessity

Not necessary as a nutrient - body can manufacture it from carbohydrates as needed.

In healthy foods (eg. fruits), it is an unavoidable ingredient.

As Poison

In modernly common contexts, sugar is a poison.

Further complications include: higher blood pressure, higher trglyceride levels, lower HDL cholesterol levels, higher LDL cholesterol levels (aka metabolic syndrome), thence leading to both type 2 diabetes and heart disease (surprise!).

There are also observations leading to speculation about its role in the increased incidence of cancer with western diet/ lifestyle: insulin promotes tumor growth!