A person with almost zero sati vs A person with perfect sati

Every person has Sati. This is called the Sati as a Cetasika.

Mindfulness (sati): this is alertness, which makes us aware of what is happening to us, from moment to moment, through the five physical senses and the mind. Mindfulness is essential to insight meditation, when it must be conjoined with a clear comprehension of the suitability, purpose, and conformity with reality of any action. Then it is called right mindfulness (sammaa sati). Usually the average person acts without any form of mindfulness; his acts are prompted by force of habit. Right mindfulness has two functions: one is to increase the power of recollection and the other is to evaluate what is wholesome and what is unwholesome. Right mindfulness is a spiritual faculty that maintains a proper balance of the other faculties — faith, energy, concentration and wisdom. https://www.accesstoinsight.org/lib/authors/mendis/wheel322.html

Then there are many levels of Sati as you progress.

https://en.wikipedia.org/wiki/Bodhipakkhiy%C4%81dhamm%C4%81

Zero sati is a sad situation:

AN8.29:7.1: Furthermore, a Realized One has arisen in the world. And a person is reborn in a central country. But they’re witless, dull, stupid, and unable to distinguish what is well said from what is poorly said. This is the seventh lost opportunity …

Yet there is also wrong mindfulness, attending to the unskillful:

AN10.119:12.1: ‘Wrong mindfulness has a bad result in both this life and the next.’

Right mindfulness is described here:

SN45.8:9.1: And what is right mindfulness? It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of desire and aversion for the world. They meditate observing an aspect of feelings—keen, aware, and mindful, rid of desire and aversion for the world. They meditate observing an aspect of the mind—keen, aware, and mindful, rid of desire and aversion for the world. They meditate observing an aspect of principles—keen, aware, and mindful, rid of desire and aversion for the world.

A simple example of wrong mindfulness is texting while driving. Minding the text is wrong while driving. It kills people.

Another example is alcohol or drugs, which impair the attentiveness that is the foundation of mindfulness:

AN5.174:8.1: Anyone who uses alcoholic drinks that cause negligence creates dangers and threats both in the present life and in lives to come, and experiences mental pain and sadness. Anyone who refrains from using alcoholic drinks that cause negligence creates no dangers and threats either in the present life or in lives to come, and doesn’t experience mental pain and sadness.

Zero sati would be insanity: breaking precepts, acting on every urge... A person with zero sati would have less control than that of an animal

An anagami has perfect sati. In fact, an anagami is considered one perfected in consideration. Thus, one with perfect sati would have no desire or aversion: they would be entirely dispassionate.

Here from the Sutta

The Blessed One said, "Suppose, monks, that a large crowd of people comes thronging together, saying, 'The beauty queen! The beauty queen!' And suppose that the beauty queen is highly accomplished at singing & dancing, so that an even greater crowd comes thronging, saying, 'The beauty queen is singing! The beauty queen is dancing!' Then a man comes along, desiring life & shrinking from death, desiring pleasure & abhorring pain. They say to him, 'Now look here, mister. You must take this bowl filled to the brim with oil and carry it on your head in between the great crowd & the beauty queen. A man with a raised sword will follow right behind you, and wherever you spill even a drop of oil, right there will he cut off your head.' Now what do you think, monks: Will that man, not paying attention to the bowl of oil, let himself get distracted outside?" "No, lord." "I have given you this parable to convey a meaning. The meaning is this: The bowl filled to the brim with oil stands for mindfulness immersed in the body. Thus you should train yourselves: 'We will develop mindfulness immersed in the body. We will pursue it, hand it the reins and take it as a basis, give it a grounding, steady it, consolidate it, and undertake it well.' That is how you should train yourselves." - sn22.48

This from abhidhamma

Therein what is faculty of mindfulness? That which is mindfulness, constant mindfulness, recollection, mindfulness, act of remembering, bearing in mind, non-superficiality, non-forgetfulness, mindfulness, faculty of mindfulness, power of mindfulness, right mindfulness. This is called faculty of mindfulness.

Mindful.’ Herein, what is mindfulness? That which is mindfulness, recollection, recall, mindfulness, remembrance, bearing (in mind), not losing, not confusing, mindfulness, the Faculty of Mindfulness, the Strength of Mindfulness, Right Mindfulness: this is called ‘mindfulness.’

With this mindfulness he is endowed, truly endowed, having attained, truly attained, being possessed, truly possessed, furnished (with it). Because of this ‘mindful’ is said. - vibhanga