Is claiming to be threatened to death or torture for political or religious beliefs without any supporting evidence that shows it actually happened (from a country which is prone to, and known for torturing, kidnapping and killing political oppositions without leaving traces) enough to get refugee status(get accepted as a refugee) in another country?
If the intent is to come to the US, you need to show that you are a refugee, that you need to be resettled, and that you are not inadmissible to the US – you might then be eligible for referral to the US Refugees Admissions Program. The referral might be by UNHCR (mostly), perhaps a US Embassy, or a qualified NGO. As a terminological matter, if you are already in the US, you apply for asylum, not refugee status. Either way, you have to show that you are unable or unwilling to return to your home country because you have been persecuted there in the past or have a well-founded fear that you will be persecuted if you go back, and that your persecution is connected to your race, religion, nationality, membership in a particular social group, or your political opinion. Your fear of future persecution must be "well-founded", and read INS v. Cardoza-Fonseca, 480 U.S. 421 to see what that means.
Establishing a "well-founded fear" of persecution is a lower burden than establishing that it is "more likely than not" that there will be persecution. If you are in the US and are applying for asylum, you only need to establish a well-founded fear of persecution. In that instance, Cardoza could establish that her brother had been tortured by the Sandinistas, but could not establish any actions by the government against herself. The immigration judge applies a "clear probability of persecution" test and found her case wanting: SCOTUS determined that the proper standard is "well-founded fear", based on the statutory definition of "refugee".
But ultimately, someone has to judge what constitutes a well-founded fear. It should be noted that under 8 USC 1158, "The Secretary of Homeland Security or the Attorney General may grant asylum", and nowhere does it say that asylum must be granted.
That depends on the desired destination country. In most it probably then depends on a judgment call by a local official. In the US that official is likely to be an Immigration Judge, or possibly an official with Customs and Immigration.