Start here:

• The case for suffering-focused ethics (Lukas Gloor, 2016)
• Risks of astronomical future suffering (Brian Tomasik)
• Are happiness and suffering symmetric? (Brian Tomasik, 2015)
• Reducing long-term risks from malevolent actors (Althaus and Bauamann, 2020)

Further reading:

• The horror of suffering (Brian Tomasik)
• The world destruction argument (Simon Knutsson)
• How important is experiencing suffering for caring about suffering?
• Tranquilism (Lukas Gloor, 2017)
• Cause prioritization for downside-focused value systems (Lukas Gloor)
• Does Negative Utilitarianism Override Individual Preferences? (Brian Tomasik)
• Why I’m not a negative utilitarian (Toby Ord)
• Thoughts on Ord’s Why I’m not a negative utilitarian (Simon Knutsson)
• Are pleasure and pain equally energy-efficient? (Carl Shulman, 2012)
• Reply to Shulman’s Are pleasure and pain equally energy-efficient? (Simon Knutsson, 2017)
• Reducing risks of astronomical suffering: a neglected priority (David Althaus and Lukas Gloor, 2016)
• The importance of wild-animal suffering
• The importance of insect suffering
• The unproven and unprovable case for wild-animal suffering
• Is there more suffering than happiness in nature? A reply to Michael Plant
• Breeding happier animals (Carl Shulman)
• Academic bibliography on suffering-focused ethics