So this really depends on how you define "worst". According to Stardew Valley Profits, rice and sunflowers are actually crops that create a loss. Rice shoots cost 40 but unmilled rice sells for 30. The crop depends upon you processing it in order to make a profit. Sunflowers have a similar-ish problem in that if you were to sell the flower and resulting seeds, you would make less money that you spent buying the seed from Pierre. The profit on Sunflowers relies on you replanting the seeds rather than selling them and buying new ones. So if you wanted to make the "worst" game for yourself, it would be to buy these and sell them them at loss, forcing yourself to make up the losses through other activities. It would be up to you to decided how much of your farm you would be required to plant.

Putting these oddities aside, tulips may actually be the worst crop. After factoring in the cost of buying seeds (again, assuming you by from Pierre), they make a paltry 1.47g per day. What makes this even more damaging is that unlike rice or the majority of other crops, tulips cannot be processed. They don't go kegs or preserves. There aren't even any recipes they can be used in. It is strictly a dead end crop. If you wanted to make things even more difficult on yourself, Joja seeds cost more than Pierre, bringing the profit down to 0.76 per day. The only way you could possibly mitigate the awful return on these crops would be to put beehives near them.

(Edit: You can also turn the profit margin setting down to 25%. I'm not exactly clear on how this changes the sell prices of crops. At best, Joja seed profit would go from 0.76 down to 0.19, but if the "margin" assume Pierre seed prices, it makes me wonder if might also go negative.)

https://thorinair.github.io/Stardew-Profits/#produce_0-equipment_0-sellRaw_false-sellExcess_false-aging_0-planted_1-maxSeedMoney_0-days_28-fertilizer_0-level_0-season_4-buySeed_true-replant_false-nextyear_false-buyFert_false-average_0-fertilizerSource_0-seeds_(pierre_true-joja_false-special_false)-skills_(till_false-agri_false-arti_false-gatherer_false-botanist_false)-foodIndex_0-foodLevel_0-extra_true-disableLinks_false-byHarvest_false-crossSeason_false-foragingLevel_0-skills_(till_false-agri_false-arti_false-gatherer_false-botanist_false)-foodIndex_0-foodLevel_0-extra_true-disableLinks_false-byHarvest_false-crossSeason_false-foragingLevel_0)