Straight from the wiki: "He is still reasonably frightened of danger that is beyond his ability though, such as Luffy and Zoro popping the coating bubble while deep under the sea or the White Strom, or when traveling on Green Bit when he was adamant that he and Robin stay close together. His "I-can't-go-on-this-island-or-I'll-die-disease" is still the same as shown when he did not want to go to Punk Hazard, even despite the fact he understood the strength of his crew members." Lemme keep going: "Even though he claimed to have graduated from the Weakling Trio after his return to Sabaody Archipelago, Usopp has shown to retain his cowardly personality especially when it comes to foes with a fearsome reputation. After Luffy formed an alliance with Law, Usopp was extremely pessimistic at the idea of making enemies out of Kaido. At Dressrosa, Usopp only wanted to destroy the SMILE factory without confronting the Donquixote Pirates even after hearing about the atrocities they committed. During Operation S.O.P. at the underground trade port, Usopp showed a moment of weakness when he was fleeing from Trebol and nearly abandoned the dwarves. Because of his own cowardly nature, Usopp is sympathetic towards the plight of Law's captured crewmates at Wano and would not fault them if they did reveal Kin'emon's plans to the Beasts Pirates as he would do the same if he was in their position. While he understood Shinobu's frustration about the leak of Kin'emon's plans, he was still disturbed by her suggestion of silencing the captives.
Usopp is always in favor of doing to things the "easy way". Whenever the crew is forced to take the high risk path, Usopp panics and loudly complains about it." I can still see Luffy screaming when he was facing someone stronger than him. Or Roger, or Rayleigh, or BM, or Kaido. All of them being scared at the same time.