"Hard to kill" usually means "tolerates being forgotten". That is the wrong test, because most houseplants do not die of being forgotten. They die of being fussed over.
The plants below are forgiving of the specific mistakes beginners actually make: watering too often, not enough light, and a cold room in February. Each one is listed with the thing that will still kill it, because everything has a limit.
1. Snake plant, Dracaena trifasciata
Thick upright leaves that store their own water. Happy in low light, happy in bright light, happy if you go away for a month.
Still kills it: watering on a schedule. In winter it wants water roughly once a month. Weekly watering rots the base.
2. ZZ plant, Zamioculcas zamiifolia
Glossy leaves and underground rhizomes that hold weeks of water. It will sit in a dim office corner and look deliberate.
Still kills it: a pot with no drainage. The rhizomes turn to mush and you will not see it until the stems yellow and fall over.
3. Pothos, Epipremnum aureum
The vine everyone starts with, and for good reason. It grows fast enough that you can see what it thinks of a spot within two weeks, and it wilts dramatically when thirsty and recovers within hours.
Still kills it: very little. Cold water and a cold draught will spot the leaves. It will survive that too.
4. Heartleaf philodendron, Philodendron hederaceum
Softer leaves than a pothos and slightly more tolerant of low light. Trails, climbs, roots from a cutting in a glass of water in ten days.
Still kills it: sitting wet in a cold room. Warm and wet it forgives. Cold and wet it does not.
5. Spider plant, Chlorophytum comosum
Fast, cheap, and it tells you what is wrong. Brown tips mean dry air or fluoride in tap water. It throws out babies when it is happy, which is a satisfying way to find out.
Still kills it: long periods bone dry. It bounces back from one drought, not from six.
6. Cast iron plant, Aspidistra elatior
Named for exactly this. Deep green leaves, tolerates genuine gloom, tolerates neglect, tolerates a cold hallway.
Still kills it: direct sun, which scorches it, and overwatering. It grows slowly, so it uses water slowly.
7. Peace lily, Spathiphyllum wallisii
The most legible plant on this list. It collapses theatrically when thirsty and stands back up within an hour of watering. If you want feedback, this is the one.
Still kills it: letting it collapse repeatedly. Each full wilt costs it root tissue. Also note it is toxic to cats and dogs.
8. Chinese evergreen, Aglaonema commutatum
Patterned leaves, low light tolerant, slow and steady. The silver and green varieties handle dimmer rooms than the pink and red ones, which want more light to keep their colour.
Still kills it: cold. Below about 15C the leaves go translucent and mushy. Keep it off winter windowsills.
9. Rubber plant, Ficus elastica
The one fig that is not temperamental. Thick waxy leaves, grows into something substantial, and it does not drop everything the moment you move it the way a fiddle leaf does.
Still kills it: a wet pot in low light. Give it bright indirect light and let the top third dry out between waterings.
What they have in common
Every plant on this list tolerates drying out and none of them tolerate staying wet. That is not a coincidence. It is the single most common way a houseplant dies, and the whole list is chosen around it.
Which means the one thing worth knowing at any given moment is how wet the soil actually is. That is the reading the FACEPLANT Pot shows on its face, and the tank underneath means the plant takes what it needs rather than what you guessed. Pick the species in the app and the pot judges it against the right range, because a snake plant and a peace lily should never be held to the same number.
The short version
If you have killed a few, you have almost certainly been too generous. Start with one of these, let it dry out between drinks, and give it a month before you decide you are bad at this.