Impact of detergent on internal living tissue?
Caustic Ingestion Injury
Triton X-100 has a pH of 9.7 at 100% concentration (according to Wikipedia) which can cause alkaline caustic injury, however it is less likely to cause severe full thickness injury, as those injuries tend to happen with ingested products of pH &lt;2 or &gt;12.5 or with other corrosive properties that Triton X-100 does not have. Ingestions at pH 6.0-8.0 are unlikely to cause injury unless there is long term exposure (as in gastro-oesophageal reflux disease or bile reflux); note that saliva itself often has a pH of 7.8!
Alkaline caustic injury has a large spectrum. The alkali can cause liquefactive necrosis via saponification and protein dissolution. In the best case scenario, there is only superficial injury to mucous membranes, causing pain and exudates. In the worst case scenario there is full thickness involvement, usually involving the oesophagus, where you get a perforation. One of the worst cases I have had any involvement in was a young lady who drank a large quantity of Drano (concentrated NaOH with pH 11.5-13.5) and had oesophageal, gastric and duodenal perforation with extensive chemical damage to her pancreas, liver and fortunately to a much lesser extent, mediastinum.
For reference, Zargar's grading system for caustic ingestion (usually based on findings on gastro-oesophagoscopy +/ pharyngolaryngoscopy) is as follows:

Grade 0: Normal examination
Grade 1: Oedema and hypermia of the mucosa
Grade 2a: Superficial ulceration, erosions, friability, blisters, exudates, hemorrhages, whitish membranes
Grade 2b: Grade 2a plus deep discrete or circumferential ulcerations
Grade 3a: Small scattered areas of multiple ulceration and areas of necrosis with brown-black or greyish discoloration
Grade 3b: Extensive necrosis

Triton X-100 would most likely cause Grade 1-2b injury. Grade 3 injury is unlikely but I suppose it depends on dose as well.
Ingestion at lower concentrations and effects not related to caustic ingestion:
This link contains information on the general toxicity of non-ionic surfactants such as Triton X-100.
In summary:

They cause mild irritation to mucous membranes
This is primarily due to foaming
Foaming and irritation can cause vomiting and diarrhoea
Foam can also be aspirated causing chemical pneumonitis
Alcohol ethoxylates (as Triton X-100 appears to be) are readily absorbed into the bloodstream via mucous membranes and is likely to have toxic effects in this way

The rest of the evidence I could find also states:

They can cause haemolysis- makes sense, as surfactants in the circulation would come into contact with red cell membranes
Triton X-100 causes direct cytotoxicity due to cell membrane disruption
It also inhibits NAD(P)H, which is a coenzyme involved in cellular respiration
There is dose-dependent destruction of the cytoskeleton
There is also some associated double-stranded DNA breakage
It is possible for cells to recover from this poisoning

Thus, the likely scenario from swallowing dilute Triton X-100 is this:

First you get foaming, oral &amp; oesophageal pain and abdominal pain
Next you get vomiting and diarrhoea, at which point you may inhale some of the foam
If you've inhaled any foam, you develop respiratory distress
You develop dose-dependent haemolysis which presents as tiredness (and/or shortness of breath, chest pain, palpitations), red or dark brown urine, jaundice
In severe cases potential multi-organ failure as a result of direct cytotoxicity, haemolysis, anaemia and/or chemical pneumonitis

It seems it'd be a huge spectrum all the way from general foaminess and some pain all the way to multi-organ failure and death. I'm not entirely sure what doses would be toxic as it appears no-one has forced animals or humans to drink the stuff!
Regarding whether there are more toxic and corrosive but chemically similar compounds out there
yes.