Interspecies Conflict/big cat
1) 300kg smilodon fatalis vs 300kg barbary lion
2) 300kg smilodon fatalis vs 350kg xenosmilus
3) 350kg xenosmilus vs 400kg american lion
1) 300kg Smilodon fatalis vs 300kg Barbary lion: Smilodon fatalis was intermediate in size among Smilodons (Smilodon populator being the largest; Smilodon gracilis being the smallest). It is famous for its long upper canines (over 25cm) and powerful, stocky build. Smilodons killed prey by ambush; wrestling them to the ground to deliver a stabbing bite to the throat or belly to induce blood loss. Barbary lions were large, thick-maned lions that preyed upon various cervids and suids. They were slightly shorter than modern-day lions (shorter legs), had shorter muzzles, and longer bodies. The Smilodon's more powerful build will give it an edge in the positioning battle with a Barbary lion, and its chances to effective utilize its bite will be greater because of this. Both can win, but edge to Smilodon fatalis.
2) 300kg Smilodon fatalis vs 350kg Xenosmilus: There's not a great deal of information on Xenosmilus, but from what has been determined so far, it was a formidable animal. Xenosmilus was a very muscular felid that resembled the Smilodon in a few ways (powerful build, prominent canines, etc.), but was different in other ways. One of the differences was its bite. While the Smilodon's "sabers" were made to impale a soft tissue area (throat, belly) to induce blood loss (after which the Smilodon may have disengaged to wait for the prey to bleed to death), the Xenosmilus had shorter canines designed to remove flesh with each bite. Xenosmilus likely had the same ability to wrestle prey items to the ground that Smilodon had (good range of motion in the shoulder joints), but its bite didn't need to be as precise. Tough fight between 2 formidable felids, but the size advantage of Xenosmilus will help it force the position it wants most of the time. Edge to Xenosmilus.
3) 350kg Xenosmilus vs 400kg American lion: The American lion was one of the largest cats to ever exist (along with Smilodon populator). Its build was designed more for running than its modern-day counterparts, and it preyed upon bison, horses, ground sloths, camels, deer, & other large mammals. In this battle the American lion will have a decent weight advantage (and larger jaws), but it probably won't be enough to consistently offset the stockier, more powerful Xenosmilus in a battle for position. The American lion will likely have the reach advantage in a "swipe war", but the more dangerous bite of the Xenosmilus will also likely be a decent difference-maker. Close to 50/50.